Ducati Monster Forum

Fitting these dirt bike Keihin FCR MX 39 carbs to my 750 Monster. MX style flatslide carbs have a choke (unlike Ducati specific Keihin flatslide carbs), dont freeze like stock CV carbs and usually have adjustable accelerator pumps. So who wants flatslide performance with a choke and without selling a kidney?

The carbs I purchased are used and are side draft items, but they are cheap and plentiful from dirt bike yards. Being side draft carbs means friggin' around with the manifolds, pod filters, 2 into 1 throttle cables, etc.

Some assembled parts so far.

(https://live.staticflickr.com/65535/49457535996_9be183c26e_h.jpg) (https://flic.kr/p/2imoNnS)20200129_121203 (https://flic.kr/p/2imoNnS) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

I have plenty of jets and some needles which will work for a 750.


(https://live.staticflickr.com/65535/49462568256_886cb63497_h.jpg) (https://flic.kr/p/2imQAhY)Mikuni-45-degree-rubber-sleeve (https://flic.kr/p/2imQAhY) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr
(https://live.staticflickr.com/1901/31562700688_e04a5f1626_h.jpg) (https://flic.kr/p/Q666hC)20181005_115746 (https://flic.kr/p/Q666hC) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr
(https://live.staticflickr.com/65535/49453007351_f96f11ef00_w.jpg) (https://flic.kr/p/2ikZAaM)images (2) (https://flic.kr/p/2ikZAaM) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr
These are new, mine are going to be crusty. One is off a Husky and one from a KTM. They are slightly different but both side draft with TPS and choke and one has a hot start knob. One is more this style
(https://live.staticflickr.com/65535/49453239527_44ed3705d7_m.jpg) (https://flic.kr/p/2im1MbP)images (3) (https://flic.kr/p/2im1MbP) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr(https://live.staticflickr.com/65535/49452522158_b777210a00_w.jpg) (https://flic.kr/p/2ikX6Wo)images (https://flic.kr/p/2ikX6Wo) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

Some of the MX carbs have cast bell mouths like the one above, so I avoided them. I was hoping for 37mm carbs, but 39mm carbs were available with bolt on velocity stacks/airbox adaptors. This gives me options to mix and match parts I already have. I'm trying to do this cheap, simple and functional.

 Both carbs will face forward and be in a similar postion to the stock carbs except that they will be horizontal. The rear cylinder carb will sit on a modified manifold and the front cyl carb will have 45 deg manifold rubber to level it.

More updates to come.

Looking at a throttle kit like this from Powerbarn. It works with split FCRs for big KTMs. The Ducati version are on their way.

http://power-barn.com/motion-pro-throttle-cable-set-for-ktm-950-adventurer-with-keihin-fcr/
(https://live.staticflickr.com/65535/49465558878_b629c5faa1_n.jpg) (https://flic.kr/p/2in6Viq)a207919132a89fe885605d_l__60861.1415401385.386.513 (https://flic.kr/p/2in6Viq) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

(https://live.staticflickr.com/65535/49466721468_1c1eb5c004_h.jpg) (https://flic.kr/p/2incSU5)s-l1600 (1) (https://flic.kr/p/2incSU5) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

Red knob is hot start, flood start. Choke hidden behind it.
(https://live.staticflickr.com/65535/49467490192_e4d6a423d3_h.jpg) (https://flic.kr/p/2ingPpW)s-l1600 (4) (https://flic.kr/p/2ingPpW) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

(https://live.staticflickr.com/65535/49466732873_35328647ff_n.jpg) (https://flic.kr/p/2incWhH)s-l300 (5) (https://flic.kr/p/2incWhH) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr


These two carbs above are the actual carbs I purchased. 2005 and 2009 models. You can see they are a generation apart MX models, one slant body side draft and one later straight body side draft. As they both will face forward they will have different clearance from the frame struts in the vicinity.  I will remove the tps for now as the aggressive oem Kokusan ignition suits the stock low compression motor. Running an Ignitech programable ignition and tps is another project for another day.

(https://live.staticflickr.com/65535/49474795217_443d3482b7_n.jpg) (https://flic.kr/p/2inVfWD)a20792012e8af9235892cd_l__83734.1415401439.386.513 (https://flic.kr/p/2inVfWD) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

These will be handy and save me buying new filters. They are a low cost solution with a nice shape for flow.

(https://live.staticflickr.com/65535/49474162178_805754fe3c_m.jpg) (https://flic.kr/p/2inS1Lb)a20791913210eb4a41e6a_m__55419.1415401402.386.513 (https://flic.kr/p/2inS1Lb) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

These adjustable slow air jet screws are absolutely worth their bloody weight in gold (but cheap to buy).

Phenomenal gift to tuners!

Sure is mate. The way the SAJ screw overlaps with the pilot jet, IMS, needle root diameter and slide cutaway means it can be used to cover a multitude of sins ;D. I like how it lets you choose the off/on throttle character you prefer at smaller throttle range. But of course you know all that I'm stating the obvious because most people have no idea how powerful (Speeddogs words) a little component it is.

I've organized a mate to cut and machine a couple of manifolds so I have options for the rear cylinder carb.  The top of the rear Cyl carb must clear the rear frame spar and the float bowl has to clear the forward struts. The manifolds have subtle differences in angle and length giving some options for a good fit. I'm starting to get excited.

(https://live.staticflickr.com/65535/49484986512_aa30362ca8_h.jpg) (https://flic.kr/p/2ioPusC)20200204_080719 (https://flic.kr/p/2ioPusC) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

First carb being prepped. Only one leak, not bad.
If I'm happy with the outcome I'll offer a kit to customers, but once again I'm answering questions no one is asking (or 20 years too late). Having fun though  :D

(https://live.staticflickr.com/65535/49487160451_ea599af5ff_h.jpg) (https://flic.kr/p/2ip1CGk)20200204_220441 (https://flic.kr/p/2ip1CGk) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

First and second gen MX FCR's. First gen on the right. It's familiar to us road guys as its a road race carb modified for MX. Second gen on the left has a broader body with more parts encapsulated internally to protect them from mud. All the jets and needles are the same except the pilot jets due to the different float bowl design.

(https://live.staticflickr.com/65535/49486665393_6af65eaa80_h.jpg) (https://flic.kr/p/2ioY6wR)20200204_220422 (https://flic.kr/p/2ioY6wR) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

Heres another pic showing the differences yet they are internally functionally identical except for the float bowl which has resulted in very different looking pilot/slow jets.

(https://live.staticflickr.com/65535/49486650378_c0fda77c63_h.jpg) (https://flic.kr/p/2ioY24Y)20200204_215805 (https://flic.kr/p/2ioY24Y) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

The slow jet many of us know on the right is also used in Harley butterfly carbs.  The jet on the left is from the 2nd gen MX carb. Are these jets calibrated on the same scale? I'm guessing yes. Can anyone confirm this as all the other jets are the same? Jet on the left is a 42 one on the right is a 52. Bore size fits the relative size too by sight. Jet cleaning tool also confirms that the 52 is larger, but are they drilled to scale?

These are the N424-21(long) Vs N424-25B(short)

I think they're both to the same scale, one way or another.
It's what I'd do, given the opportunity.

My suspicion is that they are drilled to the same scale.
Likely 0.42mm and 0.52mm diameter holes.

Or they flow them on some apparatus and they flow 42/52 grams of molasses per fortnight at 53.7 degC.

Thanks mate.  :) Good to get your opinion. My hope was that the only difference was length for reach into the deeper float bowl design.

From my staggeringly large selection of Keihin pilot jets:

#62 - 0.0238" drill shank will pass thru, 0.0248" will not.
So hole is between 0.604mm and 0.630mm.

#60 - 0.0238" will *almost* go through.
So hole is very nearly 0.604mm.

#52 -  0.0200" will pass, 0.0208" will not.
so hole is between 0.508mm and 0.528mm.

Not much of a sample size, and it's only the 'short' variety, but I'd bet money.

Cool project, I just got a bike and had posted about the exact same idea, seems like it should work fine  ???

https://www.ducati.ms/threads/keihin-carbs-anyone-tried-an-oem-version.725957/

#62 = 0.62mm
#60 = 0.60mm
#52 = 0.52mm

The numbers aren’t random.  ;D

I'm glad they're not Mikuni TM 38's with a wildly different jetting scale to BDST38's or anything else on the planet [bang]

My concern is fitting these carbs and their filters between the frame spars. The 2nd gen carb is fat. It's pretty tight.

It's good news for sure. I'm hoping to not have to play with float levels too much, it's a great way to go mad. ;)

Ordered the jet from the importer who confirmed the same  size scale. Not far from mock up fitting stage. I'll dremel out the 45 deg manifold boot a little for the spigot to fit.

Some more parts from Powerbarn.
http://power-barn.com/motion-pro-straight-push-pull-throttle-assembly-01-0073/
http://power-barn.com/motion-pro-push-pull-throttle-cable-set-for-ducati-with-keihin-fcr-and-fcr-singles/

https://www.mikunioz.com/shop/tm38-twin-mikuni-flatslide-kit-ducati-860-900-desmo/?v=6cc98ba2045f

Above is the back up plan option if the large bodied FCRMX carbs dont fit in the confines of the Monster frame. Im confident they will fit in a Supersport frame. The FCR's have accelerator pumps and roller slides, these TM's don't.

https://www.mikunioz.com/shop/tm38-twin-mikuni-flatslide-kit-ducati-860-900-desmo/?v=6cc98ba2045f
Nice price!

And our Pacific Peso is weak, good for you guys.

A question. What are the ID measurements for each end of efi manifold rubbers for 695, 696, etc with the regular 45mm throttle bodies? Maybe these can be cut to suit the 48mm OD of the FCR spigots for the front cyl to get the horizontal angle.  I ask remembering that Chris (CCW), once mentioned seeing FCR's fitted to 1000DS manifolds.
I also thought of using automotive 45 deg inlet hose.

This critter?

(https://live.staticflickr.com/65535/49518038201_e8dc83a92a_z.jpg) (https://flic.kr/p/2irJTzk)

Thanks, yeah [thumbsup]. Could I cut it off the alloy section and clamp it to the front cylinder manifold to get close to horizontal? Or even use the TB to airbox rubbers cut down?

It's an aluminum part with the rubber cast/molded/vulcanized over it.

34.3mm ID where it mates to the head, 48.6mm ID on the straight bore in the rubber.

~47.3mm diameter on the.... anti-groove(?) part.

There's at least 2 different versions, I suspect small block/big block like carbie manifolds are.

You reckon its about a 15-20deg bend? The TB to airbox rubbers are more like 45 deg, but are they stiff enough and sufficiently petrol resistant?

Unfortunately the 45 deg biscuit needs a little too much reaming. Not impossible, but annoying.

(https://live.staticflickr.com/65535/49524604492_222ba340d0_h.jpg) (https://flic.kr/p/2isjxvf)20200212_173234 (https://flic.kr/p/2isjxvf) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

I got the bikkie to work by reaming it out with the die grinder, sandmop and elbow grease. It's on firmly.

(https://live.staticflickr.com/65535/49524386531_5474cadf34_h.jpg) (https://flic.kr/p/2isiqHi)20200212_173153 (https://flic.kr/p/2isiqHi) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

Because the cylinders are rocked back a little in the frame the 45 deg bikkie is going to place the carb very close to horizontal and within its range of operation.

Sorry, missed this post.

Off the top of my head, I'd say 15-20 degrees.
But I'll check tomorrow and get a real number.

You're making good progress with the 45 degree rubber.

Thanks mate, appreciate your help. I was concerned that I would have to remove too much material and render the 45 deg boot useless. Fortunately the silicon content makes it hang on tight and conform well to a slightly larger object. The vertical cyl manifold is being cut and machined to run straight out of the cylinder under the cross brace with enough clearance when the oem spigot rubber is added. I'll end up running the carbs on the cylinders which give the best clearance. I'm concerned about the sheer bulk of the later gen MX carb. It's a big rig.

A question about the float bowl vents, each carb has four which is a touted feature. Are they really vents or extra overflow ports for the inevitable dirtbike tip over. I think the latter. They are on T fittings/junctions, so I have plugged two vents of the four so that I can reduce hoses leaving only the float bowl overflow hoses. I plugged the vents that could face wind turbulence, leaving those that face down or rearward. I would block them all if anyone could confirm it would be ok.

Float bowl needs a vent.  No idea of anything else.

IMO, I think you're correct, overflow for tipovers.

Float bowl needs a vent to ambient air pressure that's not subjected to wind, that's all.
In normal running there's no filling or draining of the float bowl that's fast enough to need multiple vents.

It's interesting how the road bike FCR's don't have extra vents, although the one shared on tandem FCR's is quite a large volume pipe. The tandem FCR's on Ducati's don't have traditional overflow vents from the bottom of the float bowl like OEM CV carbs, but these carbs do. That makes five small vents per carb with one designated for conventional float bowl overflow. With any serious flooding will the conventional vent be enough? I'll keep an eye on that. I have capped the forward and side facing vents to protect them from wind. If I can get away without extra vent tubes I will.

Offset due to big-block cylinders being taller, IIRC it's 10mm:

(https://live.staticflickr.com/65535/49526914123_7bd2dc1d46_o.jpg) (https://flic.kr/p/2iswo5t)


Apparently the big-block heads have slightly longer intakes, the corresponding manifolds are ~4mm shorter.

(https://live.staticflickr.com/65535/49527424211_efda8d45c7_b.jpg) (https://flic.kr/p/2isyZH6)


Total bend angles are quite close.

(https://live.staticflickr.com/65535/49526913508_d61f5bfc6d_z.jpg) (https://flic.kr/p/2iswnTS) (https://live.staticflickr.com/65535/49527424431_7b48ab5a95_z.jpg) (https://flic.kr/p/2isyZLT)

Cheers.
That's a handy little device :D

  (https://live.staticflickr.com/65535/49531674198_bc47cfb79d_w.jpg) (https://flic.kr/p/2isWM5J)photo-134-400x400 (https://flic.kr/p/2isWM5J) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

     (https://live.staticflickr.com/65535/49532371527_f48417e933_h.jpg) (https://flic.kr/p/2it1mnD)Mikuni-VM-TM-2-1-cable-set-w.-Quick-Action-Throttle (https://flic.kr/p/2it1mnD) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr



This combo of TM36 and 2 into 1 throttle for about $510 Oz. An option for a 600 or 750 as there is no accelerator pump, I would opt for the smaller sizes, so 36mm for the 750 and 38mm for the 900. Go bigger and you need the FCR's with acc pump (which are the same price used) in 39 and 41mm. TM's are a cheap option however. One other thing, smaller 44mm spigots..

How is it coming along?

I haven't picked any up yet, I've got a couple other things to do first and adding power definitely is not advised. I'm a new rider and I tend to go down the rabbit hole when I buy any kind of vehicle, but you never know what you can find out there as far as deals so I figured they might be something to keep an eye out for. I've definitely been following this thread with interest.

 [thumbsup]
Cheers

Did some more work today. Careful measuring of each carb's potential position on each manifold ensued. I had to factor in the lower frame struts and the fat MX carb's giant float bowl touching one if I used it on the rear cyl horizontal manifold. That carb's position will be lower. I also considered the position of the throttle cables, choke knobs, float bowl vents, idle speed knobs, fuel lines, main jet access cap, oil cooler lines, air filters and the drain hoses. The carb heating kit will be removed and replaced with the oem oil cooler lines.

The 45 deg boot gives 20mm rise so I'll run the fat MX carb off the 45 deg boot on the front cyl manifold and put the relatively svelte slant body carb on the vert cylinder's manifold. The carbs will both face forward and be beside each other, but sit split level with the front cyl carb both higher and projected forward about 40mm. Looking at the air filters I have some more compact cone shaped K&N filters which I may have to use.
You could sink quite a few beers sitting there looking and visualising where it should all go.

Im doing this to be able to a straight carb swap.

(https://live.staticflickr.com/65535/49547497466_f5db39e24e_h.jpg) (https://flic.kr/p/2iukSMG)20200217_191616 (https://flic.kr/p/2iukSMG) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr
(https://live.staticflickr.com/65535/49546985233_95aada79e6_h.jpg) (https://flic.kr/p/2iuifw6)20200217_191539 (https://flic.kr/p/2iuifw6) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr
(https://live.staticflickr.com/65535/49547485611_5d034ccf38_h.jpg) (https://flic.kr/p/2iukPgi)20200217_191305 (https://flic.kr/p/2iukPgi) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

The pics of the carbs above in nearly completed form. The idle speed knobs are positioned for easy access facing out each side of the bike. I repositioned the idle speed knob of the slant carb.  Note the different manifold boots for horizontal operation. I fitted a different float bowl to the slant carb, but it has no drain outlet, so the vent breathers were given hoses to serve as overflow ports.

(https://live.staticflickr.com/65535/49547494261_1db83b7769_h.jpg) (https://flic.kr/p/2iukRQr)20200217_191459 (https://flic.kr/p/2iukRQr) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

Short vent hoses on the MX carb. It has an overflow from the base of the float bowl. One carb opens the slide clockwise and the other anti clockwise. The give away is the orientation of the carb top cap.
I will try using only the pull cable for simplicity (I always do with these carbs), but I never do that for customers for liability reasons (do so at your own risk).

(https://live.staticflickr.com/65535/49559931121_fbd193dd85_h.jpg) (https://flic.kr/p/2ivrAT4)20200220_180042 (https://flic.kr/p/2ivrAT4) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

Anyone recognize these K&N filters? They're some old ones I have cleaned up. They are 20-30mm shorter than the barrel filters (K&N RU-0800's) I have on the oem carbs. I ported one of the air filter adaptors and may use the ones that came with the carbs as they are 20-30mm shorter than the velocity stack adaptors I have ordered from Powerbarn. I really want to use the 50mm stacks and larger RU-0800 pods, but it's gonna be tight.
I'll know for sure what combination of parts to use when I go for the first fitting.

(https://live.staticflickr.com/65535/49559933231_ab75518545_h.jpg) (https://flic.kr/p/2ivrBvr)20200220_180026 (https://flic.kr/p/2ivrBvr) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

You can see the different orientation of the throttle cams from the T top caps.

Had to port this one for obvious reasons. (Ebay pic of actual carb before cleaning and porting).
Before.

(https://live.staticflickr.com/65535/49560216807_73a8915dc5_h.jpg) (https://flic.kr/p/2ivt4NF)s-l1600 (5) (https://flic.kr/p/2ivt4NF) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

After.

(https://live.staticflickr.com/65535/49560269447_9fd32a238e_h.jpg) (https://flic.kr/p/2ivtksg)20200220_184133 (https://flic.kr/p/2ivtksg) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr



This one was fine.

(https://live.staticflickr.com/65535/49560219192_592c2c72d5_n.jpg) (https://flic.kr/p/2ivt5vN)s-l300 (1) (https://flic.kr/p/2ivt5vN) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

(https://live.staticflickr.com/65535/49559537418_1468645054_h.jpg) (https://flic.kr/p/2ivpzR5)20200220_184043 (https://flic.kr/p/2ivpzR5) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr
(https://live.staticflickr.com/65535/49559539493_21608b3566_h.jpg) (https://flic.kr/p/2ivpAsR)20200220_183948 (https://flic.kr/p/2ivpAsR) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

DO35B4  and F024E4.

I think they are RU-2780.
Edit: Yes I can confirm they are. The appropriate outer covers have been ordered (RU2780DK).
So we'll see what combo of V-stack and filter fits best.

 
  [popcorn]

(https://live.staticflickr.com/65535/49591181316_1357f2fbc3_h.jpg) (https://flic.kr/p/2iycLtw)20200227_124711 (https://flic.kr/p/2iycLtw) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

With bags. This option is actually 27mm shorter than the
RU-0800's with 50mm stacks. Good to have options if things don't quite fit as expected.

G'day VE, how's it going?

VE has been working on a similar project and we have had discussions via pm. I invited VE to come aboard and share his findings. It has been great comparing notes.

  Looking good koko  [thumbsup] ... So you have decided not to use the PB-853000  ? Ive ordered a couple, from the same source, in the hope I can squeeze them in. The short bend manifold adapter I ordered http://www.nichecycle.com/ncs/categories/carburetor/flanges-adapters/carb-holder-elbow.html arrived yesterday, its quiet pliable and both ends will shoe horn onto the 46mm spigot no worries.  Im just waiting on the one into two cable and the PB-853000 before I move onto the fun part ... Great thread btw

Cheers VE.  [thumbsup]
I forgot what part that is (PB853000) [laugh]

 
 Edited that number thinking Id got it wrong , then had to change it back to what I originally wrote  [laugh] PB-853000 K&N Velocity Stack Air Filter Adapter

Oh the 50mm Powerbarn ones [thumbsup]. I think Motion Pro  make them. No they're on order with the 2 into 1 cable kit etc. Packaging considerations will determine the combination of parts to clear frame spars and struts. PB 50mm adaptor stacks, the oem 35mm adaptor stacks, RU-0800 filters and RU- 2780 filters. Mixing and matching those parts will allow a 27mm difference in length and the conical 2780's allow some lateral wriggle room. My hope is that they all fit fine and I'll use the more used parts leaving the nicer new parts for customers.

I'm watching a pair of FCR37MX carbs on eBay. I think they would work well on my stock 750 if I can epoxy or JB weld the indentations in the bell mouth, then port them. I'm open to any advice about that.

You have pics of your carbs?

(https://live.staticflickr.com/65535/49595142137_9a18f854a7_h.jpg) (https://flic.kr/p/2iyy4Tx)Fcr Mx oem (https://flic.kr/p/2iyy4Tx) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

Above is an FCR37MX carb. They came as an oem part or catalogue performance upgrade on some dirt bikes. The bellmouth is cast to the carb body, so you can't unbolt it and fit a nice filter adaptor or velocity stack.
Is it possible to fill the slots in the face of the bellmouth with JB weld or a special epoxy and then port a nice velocity stack? My concern is some of the filler medium breaking loose and getting injested.

https://www.swiftsupplies.com.au/weicon-titanium-repair-stick

Think I found the product to do the job. Any advice?

I've used the regular JB weld a bit recently, and it's pretty good.

Came highly recommended from a trusted guru.
Sticks well to intake ports.
Reportedly digestible, he cited a 2-stroke that dropped a chunk from a transfer port without damage.
Evidently it left out the pipe as dust.

It's a bit runny, so needs dams or molds if you're trying to build something like a carb bellmouth.

Thorough mixing is crucial, at least 3-4 minutes confirmed with a timer.
Mixing until the color is consistent is not adequate.

He emphasized to NOT use the fast JB.

Thanks mate. If I can do this I can port the cast stack of 37mm FCRs, which I think are a good street size for stock  750's. I was thinking of filling those slots on the face of the bellmouth and then giving the ID lip a mild radius.

My plan, run the 39s and get all the bugs out, then sell the 39s to owners of modified 750's and 900's and opt for the 37's on my 750. Im thinking maximum part throttle air velocity and response on a stock motor.

My package from Powerbarn arrived.
Modifications were necessary to suit this custom application. Mixin' n match'n the 2 into 1 throttle cables accommodates the MX carbs as the kit is for the Ducati split carb kit. A bit of friggin around, but you know whats required after the first time. The filter adaptors will also need the air jet holes drilled deeper to fit the adjustable slow air jet screws which protrude a couple of mm.

  I haven't progressed very far koko, still awaiting parts ... These are the carbs with elbows         https://ibb.co/mRqx2Kv

  [thumbsup]

If my cut n shut rear cyl manifolds dont work I'll go double elbow boots. Me mate is working out how to machine them so I may go double boots to start with. The factory must have machined them first before welding the flange on, so how does he hold it in the lathe or milling machine? He'll work out a way. With two angled boots, at least the manifolds will be closer to equal length. I'm mindful of resonance issues so well see. With that in mind an angled boot on the rear cyl manifold creates an S bend (pretty bad), but only a "curve grande" on the front cyl manifold (bad enough). I wanted to avoid an S bend creating a "water hammer" in the plumbing, it might be fine, but there's one way to find out.

Major Edit: I was able to fit the larger bodied MX carb on the rhs manifold. This makes everything easier now. I now have the option of runnjng a 45deg boot on the lhs manifold or one of the modified ones being machined to run straight.


VE, it's a good thing you got two slant bodied carbs because the fat MX type take up so much room. You have more margin for adjustment.

I have one slant body carb and one MX. With two 45 deg boots on stock manifolds they just fit. The MX carbs are about 110mm wide with a very deep float bowl. They are very large carbs.

The easy set up is two TM 36 or 38 carbs which are 75mm wide and not as long below the bellmouth, so more room side by side and more clearance above frame struts. You buy two 45 deg boots, a Mikuni 2 into 1 quick turn throttle and the carbs. The issue is the jetting. Consulting Powerbarn or Mikuni Oz for a baseline is essential.

I have to decide if I should sell my FCR MX kit to a Supersport guy (easy fit) and buy the TM36 carbs or squeeze the FCR MX carbs into my M750. The FCR's are a better carb imo, but the TM's are cheap and easy to fit, the tuning will require patience however.

The air filters will be small with 45 deg boots. The conical filters just fit.

Clearance of the oil cooler lines is very close with 45 deg boots. You may have to adjust the lines a little. If Kamna sold a TDMR38 I'd fork out and buy it. I think 40mm carbs on a stock M750 is over kill, and so is the price (for me). Two TM36 carbs, manifold boots and throttle kit would come to around $600 Pacific Pesos.

I should have a modified manifold by the end of next week and this will stagger the carb back about 40mm which will help fitment. That makes me hopeful.

(https://live.staticflickr.com/65535/49650808568_17d367cf66_h.jpg) (https://flic.kr/p/2iDtnzA)20200312_214444 (https://flic.kr/p/2iDtnzA) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

Got the bastard to fit.

That’s cool right there! ^^^^   [bow_down]  Good job!

  Great news you could shoehorn it in, its looking good  [beer] ... Very interesting to see one in situ.

 I moved my oil cooler down to the lower cover many moons ago, the modified lines run low, so should be all good there  [thumbsup] 

I thought about moving the oil cooler, but left it in place as my 750 also has scrambler/adventure duties. I did have to replace the rhs oil cooler line to remove the carb heating kit.

I'm glad you have the slim slant body version, the MX version is a beast of a carb. Clearance to frame struts and oil lines, etc is in the 5-10mm range.

VE, I reckon you'll be able to use the PB velocity stack filter adaptors and larger filters because the angled boots you have are more like a 30 deg angle. The carbs will have more clearance from the frame struts and the filters will have more clearance from the front frame cross member. As long as the float angle isnt too much causing flooding those boots have advantages. I'm keen to see how you go. [thumbsup]

Check out these bad boys.

(https://live.staticflickr.com/65535/49672389072_39f31a6773_h.jpg) (https://flic.kr/p/2iFnYHf)20200318_113705 (https://flic.kr/p/2iFnYHf) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

(https://live.staticflickr.com/65535/49672101646_1657ff17d5_h.jpg) (https://flic.kr/p/2iFmvgC)20200318_113616 (https://flic.kr/p/2iFmvgC) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

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Its a tight fit for sure.
I wanted to test the concept and it ran. I have another MX wide body FCR on its way from ebay. I will have to run two of those to be able to synch them which will be by cable adjustment like the old days. So they must be matching models as the throttle cams vary in size throwing out the synch as you turn the throttle. The slant body version has the synch screw under the cap which is a bonus.
Short choke knobs are needed as there just aint enough room for the long version on the lhs carb.

My custom rear manifold will give the carbs better clearance by positioning them in a staggered formation.

Throttle slides, etc must match or synch will be trashed. I say that because I have been buying used carbs off various dirt bikes. They are cheap but there are hidden pitfalls adding to cost if you have to replace too many parts.

I will probably run two FCRMX37 or TM36 and use the 39's on a customers bike.

(https://live.staticflickr.com/65535/49672394547_4d62c1e213_h.jpg) (https://flic.kr/p/2iFo1kD)20200318_191342 (https://flic.kr/p/2iFo1kD) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

I refitted the stock carbs. I've gotta shelve the project until my machinist mate comes out of quarantine. Poor bugger.

So this is obviously a very cool project and I'm excited to see what happens since it seems like you're getting to the home stretch. You're also the one doing all the legwork and prototyping, which is the most "fun" part of a project, but at the end of the day do you think this will beat using Duc-specific FCRs?

Im only trying this because the Duck specific FCR kits have no choke and are costing well over 2 grand to buy new (1 + grand used) in local money (Aussie). The FCR kits for Ducatis are easy to fit and tune imo, so its a pity I dont live in a year round warm climate. The lack of a cold start device really annoys me ;)

Such an aptly names product!  Couldn’t tell ya how many times I’ve uttered that! LOL

 ;D

Some things to note. The MX type of FCR are very aggressive with a large diameter throttle cam making them rev very quickly as they are a dirt bike racing carb. They are the most sophisticated FCR made and reputedly designed for absolute maximum response. This would suit a track bike or balls out street bike (or gutless ol' 750 needing a wake up?). I figured they wouldnt be too much on a stock ol' M750. The slant body FCR is responsive, but allows better modulation with a smoother bottom end to midrange transition and easier to dynamically synch. I really noticed the relative behaviour of each carb on the manometer. Just did an M750 with racked 39's and it was easy since I had separated the battery box from the airbox leaving a handy gap to get to the top of the carbs.

Nice, with the Mx carbs, a lighter flywheel and clutch hud, twist the throttle and bike is gone (whilst your still hovering in the air Wylie coyote style)
 [Dolph]

So MX = motocross?

Yep. [thumbsup]

The bike came with an alloy flywheel (looks like a Nichols or Kamna). The 750 motor has a short stroke too, 61.5mm, so it spins up ok. Yeah I want a more responsive carb. [thumbsup]

 Velocity stack adapters have arrived and are a really nice fit, good to get something and not have to fettle. I think your correct about the larger filters fitting  [thumbsup]. All that's holding me up is the Venhill one into two cable, think it's held up in customs due to the virus thing, The slant bodies not having a choke isn't a prob for me, I live in a permanently warm climate. What jetting are you looking at koko ? . My engine is lightly ported with FbF 11/1 and free breathing pipes, it likes to run leaner than one would think on the oem Keihin's and K&Ns ie Main 140, slow 37.5 ... I am thinking start off approx main 145, slow 42, on the FCR, your thoughts ? ... Btw those carbs look mean sitting in there on the manifolds, wicked work  [evil]

With a mildly ported M750 with Termis, open modified air box, FCR39's, FBF hi comp pistons we are running a 52-60 pilot jet, 155 main jets,  needle on posn 3 or 4 & slow air jet screw 1-11/2 turns out there's a range of tuning to allow for fuel density variations, etc and level of porting. This local 750 has mild porting and stock cams and valves. 

Your local tuners will be more precise with jetting.

 Thanks, I have a good selection of jets, will set them up similar (52-60 pilot jet, 155 main) and go from there ... Ive become even more enthusiastic after seeing your progress  [thumbsup]

If your fuel has Ethanol you may go richer on the needle, will be interesting to see. E fuel is only a minority option here.

At least the slant body carbs will fit without a fight :D I have picked up another fat MX 39 and are looking for another slant bodied dirt carb for two complete pairs. That should give a set each for myself and a customer who is also keen to have a choke on his carbs.

If your carbs came with slow air jet screws and not the regular fixed jets then that gives you a lot of leeway to adjust out little glitches in the lower throttle range.

 Good to know, as they do have the adjustable slow air jet screws  [thumbsup] seems plenty of leeway for dialing in with these carbs ... Im up in sunny Qld, so I guess were running the same ethanol contents koko.

  As you previously stated, the banked Ducati FCR are rather costly down here in Oz (working with the ever deprecating AUD) if the graft is successful, this is a cheaper option.

E free is good. Forgot you were local. Running 98 with hi comp pistons? The bike I work on runs 98 fuel with stock ignition and no pinging.

 Yes 98, ignition is stock, apart from a set of ExactFit coils, Ive never had any pinging probs either

Picked up another slant bodied FCR39 with choke off ebay. I'll use those ol' slant body carbs and save the fancy MX's for a customer with a modded motor. The MX version are fast action with the aggressive throttle cam.  [evil] This 750 is for pillion and scrambler/wet weather duties, so I best go for the softer version.
My machinist buddy is probably flat out in the workshop during self quarantine. I'll give him a call and maybe drop off some supplies.

(https://live.staticflickr.com/65535/49696891586_6da604cf8d_n.jpg) (https://flic.kr/p/2iHxyso)s-l300 (2) (1) (https://flic.kr/p/2iHxyso) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

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Modified rear manifold. The lower lug on the cable bracket may need to be cut off, maybe. Of course business has slowed, so now is the time for projects. As we head into winter I'll do the carb swap.

(https://live.staticflickr.com/65535/49700025147_32d45a8b31_h.jpg) (https://flic.kr/p/2iHPBXi)20200326_162005 (https://flic.kr/p/2iHPBXi) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr
An oem FCRMX carb with the cast in one bellmouth filled with titanium epoxy weld. This will let me port the inside lip due to the lack of a removable velocity stack.

 The manifolds looking good, straight shooter  ;D ...  [popcorn]

If we go to stage 3 lockdown, I'll have time to take the 750 off the road to do this.

 Don't think that is far off, hope my cable shows before then  :(

Yeah, you need everything for the stage 3 lock down project. The other carb arrives Tue.

Awesome thread

(https://live.staticflickr.com/65535/49714055078_5b0394cb21_h.jpg) (https://flic.kr/p/2iK4wyE)20200330_113319 (https://flic.kr/p/2iK4wyE) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

(https://live.staticflickr.com/65535/49714914242_3b4227217c_h.jpg) (https://flic.kr/p/2iK8VXQ)20200330_113012 (https://flic.kr/p/2iK8VXQ) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

Long stack on the shorter manifold and short stack on the long manifold with 45 deg boot. An attempt to balance the manifold lengths re intake tuning. The short, straight manifold on the rear cylinder will be 40-50mm back allowing space for the longer stack and filter.

After hours of testing combinations of manifolds, boots and carb positions, I can report that I cannot get the carbs to fit. The carbs foul each other, even with the custom manifolds. I believe that Mikuni TM carbs will fit as they are 25mm and 46mm slimmer than the slant body carbs and the MX carbs respectively. The TM 36 and 38mm carbs also have their components like the choke and throttle cable in different locations giving easier clearance. They do not have accelerator pumps. There are other TM pumper carbs, but they are more expensive.
The Supersport is a better candidate for the FCR carbs.

Talk about "Sunk Costs". Should have got the Mikunis. ;D

 
 Bummer   :( ... So its a no go fitting those two slant bodies side by side, with the OEM manifolds and  45 degree elbows either ? or do they still want to  clash ?

Its very tight that way too when the carbs have chokes, but just possible. I can squeeze them in, but the lhs carb choke knob and fuel pipe boss foul unless you angle the boots outwards. Your manifold boots give more clearance from the struts and there are no choke knobs. Im concerned about the angle of the boots you're using, but if they work without float level issues, then they could be the solution for my set up.

The Supersport frame gives more options to fit the carbs in relation to each other without snagging frame spars. I might grab my mates Superlight before we go into full lockdown.

It's over to you bro and I'll be watching closely. [thumbsup]

If I lived around the corner from Buzzer or Pinion, I would have cut n shut rewelded manifolds and all would be well. [laugh] It's doable, but requires on site fabrication, TIG welding, etc that will have to wait until after the pandemic.
Doable, but not in a quick 'n dirty way.
The Mikuni TM's otoh, have their protrusions facing upward where there's plenty of room as the fuel inlet, choke and cable all exit vertically saving room between the carbs. The carb's cast bodies are narrower too and quite uniform in shape. On an unmodidied 750 I would run the little 36mm carbs as there's no accelerator pump.

 Cable arrived today, so spent a little time on the carb project

 (https://live.staticflickr.com/65535/49719338118_c718b1c92f.jpg) (https://flic.kr/p/2iKwB2y)fcr8 (https://flic.kr/p/2iKwB2y) by simon lane (https://www.flickr.com/photos/187330730@N04/), on Flickr

 Decided to lock the carbs together, thought they would be more stable that way.  Looked through my off cuts, found some 9mm and a  piece of 8mm bar. A couple of threads cut and a little filing and they are together.

 (https://live.staticflickr.com/65535/49719869061_005377ab04.jpg) (https://flic.kr/p/2iKzjRK)fcr2 (https://flic.kr/p/2iKzjRK) by simon lane (https://www.flickr.com/photos/187330730@N04/), on Flickr

 (https://live.staticflickr.com/65535/49719867171_027b6b454d.jpg) (https://flic.kr/p/2iKzjia)fcr1 (https://flic.kr/p/2iKzjia) by simon lane (https://www.flickr.com/photos/187330730@N04/), on Flickr

 They sit in there nicely ...
 
 (https://live.staticflickr.com/65535/49719870146_44253e4ed8.jpg) (https://flic.kr/p/2iKzkbs)fcr3 (https://flic.kr/p/2iKzkbs) by simon lane (https://www.flickr.com/photos/187330730@N04/), on Flickr

 (https://live.staticflickr.com/65535/49719871286_abbe988f92.jpg) (https://flic.kr/p/2iKzkw7)fcr4 (https://flic.kr/p/2iKzkw7) by simon lane (https://www.flickr.com/photos/187330730@N04/), on Flickr

 (https://live.staticflickr.com/65535/49720189657_c12e225be0.jpg) (https://flic.kr/p/2iKAYag)fcr5 (https://flic.kr/p/2iKAYag) by simon lane (https://www.flickr.com/photos/187330730@N04/), on Flickr

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Very tidy [thumbsup]

 The cable was a task, getting it so the carbs synched correctly took ages. Return cable is now obsolete, as the return springs are way strong  ;).  K&Ns are going to have to under go a little surgery, cant quiet shoe horn them in, as they are, on the long stacks ... All going to plan will drop back on it tomorrow and see how he runs.
 
(https://live.staticflickr.com/65535/49719339453_c55b10c466.jpg) (https://flic.kr/p/2iKwBqz)fcr9 (https://flic.kr/p/2iKwBqz) by simon lane (https://www.flickr.com/photos/187330730@N04/), on Flickr

Got a straight side on shot to see the angle of the carbs with those boots?

 I was just about to say to you about that :) ... I did take a pic for you but when I came in and started uploading them I realised it was crap. Will snap another for you tomorrow, there is heaps of clearance there :)  

 The bowls are at a slight angle, but I don't think its going to cause any stress ... We will find out  ;D

Those boots may be the solution, however your carbs have easy clearance from each other compared to mine. They each appear about 20mm slimmer in the body and without the protruding choke knobs. The fuel pipe boss on each carb also protrudes less. You have room to spare. [thumbsup]

VE, what is the width of each carb at its widest point? If I can use your boots then I may be able to salvage this project. I have four carbs to use so that's something. For me, it depends on how your bike runs going up steep hills ;D

Well, we're in stage 3 lock down now, with breaches enforced by the police and penalties for non compliance. No travel except for essential services work, health needs, essential shopping, welfare checks, so no riding except for travel to work. Just the excuse to take the 750 off the road to complete the carb R&D and finish some suspension work. That settles it.

I had another attempt to mix n match parts to see if I could squeeze in the FCRs. To my surprise, the fat bodied MX carbs fitted with less aggravation than the slightly narrower slant bodied carbs. The MX carbs are wider, but a solid block in shape with less prickly protusions than the slant FCRs, which foul each other. The fit of the MX carbs was still nloody ugly, with insufficient margin to frame spars to be risked for any customer. VE's manifold boots are closer to 35 deg rather than the 45 deg boots I'm using and would give the extra clearance required, but its a bloody ugly fit nevertheless. If VE's carbs dont flood or starve when the bike ascends steep hills, then it may be a solution for me cramming the MX carbs in there. If not then Mikuni TM 36 or 38 carbs are a svelte option.

Today I had a long and informative discussion with a bloke from MikuniOz, the Aust distributor. The TM non pumper carbs appear to be a real option, and an economical solution for Monster owners. I raised the issue of tuning data and baseline jetting which is the main concern for me. MikuniOz said they would provide baseline jetting and tuning support in response to my feedback. The TM 36 carbs are 440 Aud a pair with 70 odd bucks for a Mikuni quick turn 2 into to 1 throttle plus two 45 deg boots to use on the stock manifolds. Probably around 600 bucks for the lot or 660 bucks with the TM38's.

In light of this I'm tempted to use the TM's, but as I've previously mentioned, would need to decide between the 36 or 38mm carbs. With no accelerator pump, I'm wary of using the 38mm carbs on a stock 750, despite the assurances of the Mikuni rep. I don't want to have to run very rich pilot and mid range circuits to compensate for no acc pump. I'm open to people's thoughts on this.

Anyway, if I can fudge it with these manifold boots, http://www.nichecycle.com/ncs/categories/carburetor/flanges-adapters/carb-holder-elbow.html,
I'll run the monstrous MX carbs. We'll see how VE goes.

Nice.
Personally, I would go for the 36s. If they are the same body as the 38s, you could always open them up if the urge overwhelms you.
You might have a problem with a quick-turn throttle on a twin-carb setup. I tried that on my round-throttle Mikuni 36s once upon a time and switched back pretty quickly since the throttle got soo heavy.
But maybe you are much stronger than I :-)

I tend to agree, as I was leaning towards the 36mm carbs. I hate carb bog.
The 750 has standard compression (I checked), and I assume, standard cams and valves. It only has Staintune slip on pipes and a light Kaemna flywheel. It runs very well and has good response but gets breathless when really asking for performance. CV carbs annoy me.

Time for 800 heads... [evil]

Stop it [laugh]

I have 900 cams and valves..., in a box. I'm trying to ignore them, maybe down the track with hi comp pistons.

I decided to try the slant bodied carbs again. I transfered components between carbs like short choke knobs, float bowls, etc to reduce the protrusions of each carb to improve their clearance between the frame rails and each other. The carb positions are not reversable as one has wider throttle cam bracket and longer fuel inlet. Slipping my hand under the carbs allows activation of the lhs carb choke. The rhs carb choke is easily reached.
Chokes on, fuel tap on, hit the starter and it roars into life.

With much cursing and bloody mindedness the bastards fit.
(https://live.staticflickr.com/65535/49733773683_c733cc50e6_h.jpg) (https://flic.kr/p/2iLNAdB)20200404_222145 (https://flic.kr/p/2iLNAdB) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

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It's bloody tight everywhere. The carbs slightly angled upwards would solve many issues. I feel really comfortable tuning these carbs and love their performance. I hope the Nichecycle boots VE is using work well.

Congrats

Cheers.

(https://live.staticflickr.com/65535/49733771008_8177d17ba2_h.jpg) (https://flic.kr/p/2iLNzqu)20200404_222114 (https://flic.kr/p/2iLNzqu) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

I would not fit these Keihin carbs to these Mikuni 45 deg manifold boots if doing this for a customer. Maybe the boots VE is using would work better. It's too much mucking around (labour) and with too many clearance issues.

Tuning and testing next.

 [thumbsup]   And now the synking begins....


Reminds me abit when I decided on converting FCR`s from a Kwak IL4,
thinking "How hard can it be?"
Turned out not too hard but lotsa fiddling. And cheap, since I sold the other two. 8)

How sore is your forehead? ;D

Smashed from my stubborness ;)


That's the easy part. I enjoy it.

Random thought, any interest in better coils? I'll completely admit to only putzing around since I'm new but they definitely helped with start up, idle, and response (Dyna green, 8mm wires, iridium plugs). I know you're trying to baseline them for what's common on customer bikes but just wondering.

You read my mind. Once I sort these carbs I'll fit some CCW Exactfit coils I have spare. I doubt I'll be selling them anytime soon.

The stock coils actually work really well, best oem I've seen. They have enough spark to fire the plug but not so much to overwhelm the old style copper core plug wires and arc out to the frame [laugh], (thought howie would appreciate that). ;D
If I fit them, they'll need modern, well insulated plug wires or there'll be a miss at idle.

Tuned and synched the mothermake the beast with two backsers.  [evil]
Of course I allowed for the rear cylinder's bizarre S bend manifold which eccentuates having to choose where in the rpm range you want the greatest harmony. I sacrificed some synch at idle to get the best everywhere else, but the idle still sounded good to the ear so not bad.

Doing what I did by using carbs that had been single all their lives invites tuning issues like uneven component wear, strange synch baselines and different modifications. I spent four hours resolving all sorts of tuning gremlins, but finally found a decent setting. Idle knob cable length, synch setting, cable tension and assymetric manifolds all contributed idle tuning variables.

Do you have 2 separate idle knobs w this setup?

Yes, everything is separate. So I set the idle first by measuring the idle knob adjustment and carefully setting the throttle cable tension on each carb. I then set the synch and go back and forth between those adjustments and also do the idle mixture. I have an O2 tester, but I'm doing it by ear and with a manometer. It's all old school and a way to stay occupied besides watching movies, working out, reading, etc.

I will have to use different manifold boots so I'm searching for better parts that don't require modification. The process of reaming the boots has weakened them, so I can't rely on them long term.

I fitted the CCW Exactfit coils too.

I sent you an email with two photos showing how mine was mounted.  IMO, a good location for a scrambler.

Thanks Howie. Appreciate it. Replied.

Some more testing today. Got a good setting that starts easy with a few squirts of the accelerator pump and if feeling lazy one choke on that's easy to reach. Boom at the press of a button. That's how they should be sold.

Now to replace the maniflld boots, one MJ cap o-ring and possibly one float bowl gasket (it swelled up and stopped sweating).

Ok, guess which carb needed 1&1/2 turns on the idle mixture screw and which one only needed 1/2 a turn? ;)

Despite a few little bugs to iron out, I can say with confidence that the bike feels like its picked up 10 more ft/lbs of torque and 10 hp. It hasnt really, just a few hp & ft/lbs, but the response is greatly improved with better acceleration and response when you ask for it. With the light flywheel it goes great for a basically stock bike.

 

 My apologies for the late update koko ... You have come a long way since I last visited this thread, nice work. I think you will be happy with the boots, they are a good fit and easy to work with  [thumbsup]

 I did fire the bike with the new carb set up, it ran well from cold but once warm was too rich. After having a dig around in my jet assortment I realized I didn't have what I thought, so have ordered others. The Kehlin are back on there for the moment as I  needed him mobile ... Here is the pic I promised you, hope it's still of some use, the bowls are slightly angled but I think they will be ok. To find a hill would be a very long ride for me, so I don't have that particular prob .
 
(https://live.staticflickr.com/65535/49741915372_310264ee97.jpg) (https://flic.kr/p/2iMwjsy)fcr11 (https://flic.kr/p/2iMwjsy) by simon lane (https://www.flickr.com/photos/187330730@N04/), on Flickr

Thanks VE.
Interested in the gallery's opinion on the float angle. At worst a float level adjustment may be required, but it's not a severe angle. [thumbsup]

I think a float adjustment is in order...~1-2 mm I'd guess.

Float mount fore or aft in that position

Pivot mount is fore on the slant body and MX FCRs. Yes it may determine  - or +  adjustments. I'll see if the plugs and general running change and use probably only 1mm change. I think the carbs tolerance for angle is probably around 20 degrees, maybe a bit more. They are pretty level at present. I think TMs cope with about 30 and Dellortos about 40.

Check please

Some of the dirtbike guys reckon up to 30 degrees with float level changes, but that's a lot. The dirt bike carbs have float bowl baffles and extra vents to stop flooding for jumps, etc. I'm not a dirt guy so will be interested to see how they help.

(https://live.staticflickr.com/65535/49744055928_5f72c00fcd_n.jpg) (https://flic.kr/p/2iMHhLG)images (1) (https://flic.kr/p/2iMHhLG) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr
(https://live.staticflickr.com/65535/49744599631_3a29398e66_n.jpg) (https://flic.kr/p/2iML5oT)images (3) (https://flic.kr/p/2iML5oT) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

All that being said, the pilot jet will be most affected. The adjustable slow air jet screw could be tweaked 1/2 a turn here or there to compensate. Good to see such a deep main jet sitting linear to the needle jet, so no worries there.

The excellent but expensive Flatside carb solution with a choke. If I had a 900 and the Aussie dollar was strong.

 https://www.ducati-kaemna.de/kataloge/ducati/monster-750-900-1000/vergaser-zubehor-carburator-accessories/mikuni-tdmr40-vergaser-kit-fuer-ducati-900-m-ab-1993.html

Hey VE, any updates?

I can report that the carbs perform really well despite one carb having a partially blocked pilot circuit that stubbornly resists sonic cleaning. I played with the adjustable slow air jet screw and idle mixture screw as a work around. Nifty.

I was often in a higher gear using less throttle input for more response, all the more impressive since the stock CV carbs had a quick action throttle. No more whisky throttle as Speeddog calls it. The response is direct and linear with no more waiting. On more than one occasion I was in top gear thinking I was in 4th, such was the torque increase. Very impressive.

I was of the opinion that stock CV carbs posed less of a restriction to the 750 motor than the 900. I was wrong.

 [thumbsup]

  Waiting on jets atm, old carbs are refitted so he can get out on the road for some exercise ... Meanwhile the project FCR are resting  [roll]

  Your road test sounds positive, have you got/fitted the elbows ?

 (https://live.staticflickr.com/65535/49804527556_d2aed15816.jpg) (https://flic.kr/p/2iT4dSY)fcr45 (https://flic.kr/p/2iT4dSY) by simon lane (https://www.flickr.com/photos/187330730@N04/), on Flickr

I'm using the modified elbows/boots until the new ones arrive. One boot developed a rip from the clamp, so the bike is sidelined until the other boots arrive from the States. I could refit the CV carbs, but cant bring myself to do it! [laugh] I guess I'll finish all the other little details now including fitting the Ohlins shock.

That day is getting closer... ;) ;D

How much f a complete FX set?

 ;D

I'm actually quite happy with the oem Kokusan boxes on a low comp 750. The smaller bore, combustion chamber and low compression seem to work well with the aggressive advance curve angle/graph. I have only dealt with one hi comp 750 and the stock ignition worked fine with higher octane fuel. I only have one customer with a 750. The attitude is bigger is better in this wide land, but I'm a 750 convert now.
The temptation for me is using an Ignitech to facilitate a tps, and ignoring the siren call of hi comp, 900 cams and 900 valves. The original concept for the scrambler was to be able to use any fuel available in more remote areas, so standard comp is good.

More like curb :P  I wonder what a more sophisticated curve might do for pulling from low RPMs.   

Makes em real smooth.
You can even adjust the rpm while it's on the choke, totally civilized.

I certainly found that with modified 900/944's. I'm so impressed with how smooth the 750s are.

Manifold boots finally arrived from the US and were fitted.  They fitted beautifully with no modification and tilted the carbs 10-15 degrees eliminating any clearance issues. Thanks heaps mate for putting me onto these boots as they solved a lot of issues. I ordered another pair for spares.

 Excellent, pleased they did the job for you  [thumbsup] ... Will be interested to know your thoughts on float level.

 Still waiting on jets, things are moving slowly within shipping services atm   [bang] ... Will post an update when I have something

Get onto Show n Go in SA and pay for a courier parcel. [thumbsup]

Niche Cycle are a new resource, thanks again. Those boots made it easy. I'll be noting on road performance and plug colours re float level. No anomolies yet but for some internal grime in the RHS carb that wont budge despite sonic cleaning, etc. I think a high quality fuel cleaner and long ride are in order. Performance otherwise is excellent with increased response and low and mid range torque. We have effectively increased intact tract lengths by an inch or two. The lower rpm torque is very good now, but maybe with a drop off at peak rpm.  However the intake port to cylinder volume ratio has improved and maybe that will offset any peak rpm drop off. Not sure. Well see.

What jets you after?

Synched the carbs again.
1. I set the 2 into 1 cables to the same tension so the cams opened in unison.
2. I set the two idle speed knobs by eye to have the cable ends protruding the same amount (1-1.5mm).
3. Then I finished the job with the manometer to get a good setting through the rev range.
4. I had set the two idle mixture screws and slow air jet screws according to the Right Reverend Patrick Burns instructions, with the slides bottomed out.

As you can see, getting one setting wrong can shag the others. A little more complicated than the tandem carb set up.

 Thanks for the "Show and Go" tip, I will give it until the end of this month before I give up hope, if they haven't snailed their way to my door by then I will reorder from that supplier.

 Ive ordered Mains 140 ... Pilots 38 and 40 ... I understand these sound a bit small but it seems a characteristic of my motor to prefer weaker jetting, I can only put this down to the porting and manifold matching ? paradoxical as it may seem. Ive tried Mains 145 and Pilots 42, he ran well cold but was way too rich when warmed ... beyond a needle setting.

 Your observation on increased torque at lower end is interesting  [thumbsup]

 Looking forward to your long run update  :)

Must be good porting= efficiency.

My modified 900 had hi comp pistons, reworked air box, dialed cams, good valve job, very good port work and ported manifolds. I ran 50 pilot jets and could have gone to 48 in FCR 41s if it had a choke.

(https://live.staticflickr.com/65535/49987182448_5f063f1c68_h.jpg) (https://flic.kr/p/2jacnPf)20200609_213206 (https://flic.kr/p/2jacnPf) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

A much easier fit clearing the frame spar with the Niche Cycle boots. Thought I'd fit the K&N velocity stacks for pod filters while I was at it.

However, don't be heavy handed like me. Glad I got spares.

(https://live.staticflickr.com/65535/49987697176_b94189da17_h.jpg) (https://flic.kr/p/2jaf1PS)20200609_213104 (https://flic.kr/p/2jaf1PS) by Tony Kokonis (https://www.flickr.com/photos/150482584@N03/), on Flickr

I don't have anything that small for FCRs. That's more like Mikuni BDST 38 jetting IME. I wonder what needles, slow air and main air jets are supplied?

 Pilots arrived yesterday, still awaiting mains ... Which were sent separately ?  [bang].
 
 Placing a double order on the boots was good foresight ... Fitting well with the filters, I might have to  modify my filters before they fit that well. 

I usually know how it's gonna go ;D.

 I drilled out the air jet recesses another 5mm to get enough clearance or else the stacks wouldn't seat on the gasket.  I also skimmed off the lip on each stacks outer bellmouth to slip the filter on without it catching.

The front/horizontal cylinder needed a bigger pilot jet (62) in order to avoid extreme idle mixture screw and SAJ screw settings. The Vert cylinder liked a 60 pilot jet. The IMS and SAJ screws all ended up at 1& 1/2 turns each on both cylinders. I suspect a worn release plate seal in one carb or very asymmetrical manifolds, but someone has shagged the pivot arm screw so the bigger jet is a possible workaround until I can remove it without shagging the very expensive slide. If the seal is ok then it may be a function of very asymmetric intake manifolds. One thing these manifold boots do is exaggerate the difference by a long shot.
Needles raised a notch for a surprisingly major improvement in mid range performance in  both acceleration and smoothness. This bike goes better than I expected so I'm going to check the cams. I'll ask bikeboy if he has dealer records in case DP valves and cams or 900 cams were fitted in its life.

Been getting into the 20's F here. Glad the carbs have chokes.

Did some fine tuning in the idle to 1/4 throttle range (again). Adjusted the idle mixture and idle speed of each carb by ear.  Went totally old school. The bike is the smoothest it's been at low rpms and has the most even idle so far, not easy with the wildly assymmetric manifolds required to fit dirt bike FCRs . I tune carbs regularly for customers with no issue, but these well used carbs have required periodic tuning until they settled down. Despite sonic cleaning and disassembly there are some passages in one carb that have slowly cleared with use. This means the tune has changed with mileage requiring periodic carburettor adjustment. Some jobs require incremental improvement towards perfection while others land bang on target in short order.

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