I'm sure this has been covered before but I can't seem to find anything useful.
So I've been reading for 2 hours now, considering a jet kit for my 2000 M750. arrow high-mount cf slip-ons, ported/polished intake runners, slightly cut stock airbox, k&n filter.
I found what the stage 1 and stage 2 DynoJet jet kits have in them, and semi-comparable jet sizes as compared to stock sizes. they have needles, springs, and mains. same needles in both kits. stage 1 has DJ sizes of 124 and 128 main jets (~comparable to stock mikuni sizes of 116.25/120. noticibly leaner than stock???). stage 2 has DJ sizes of 144 and 148 (~comparable to stock mikuni sizes of 135/138.75. barely richer than stock???). Stock size is 132.5 from what I've found in my research. I forgot to write down my current jet sizes last time I had the carbs apart.
I can't however for the life of me find any info on what the Factory Pro jetkit includes. sooo, can someone please tell me exactly which jets and what sizes of them are included in the factory pro jet kit? specifically the CRB-D08-1.1-TI kit.
also, please share your opinions on which brand and/or stage you prefer, and why, and which you'd suggest for my setup. thanks in advance :)
or a flat out recommendation of what exact jet sizes you'd recommend for my setup, and which brand of course
I have only tuned 900s regarding specific jet sizes. Brad Black or locals like Howie may will chime in with their findings.
The FP jets are sized as stock Mikuni jets and as you note the DJ jets have their own size/flow rating numbers. A search will reveal comparison charts if you haven't already located them (you probably have).
The FP kit is very well made and comes with nice little extras like stainless allen bolts for the carbs, but the DJ kit usually has a a larger range of main jets. Some like the needle taper of the DJ better. For an open airbox consider the DJ kit for its greater range of main jets to allow for an open airbox. I haven't looked into a FP kit for 750s so contacting them is worthwhile in case they have started putting some bigger main jets in their kits.
I have frigged around with the stock Mikunis enough to drive you crazy on 900s and have a few observations. Be open to using the stock spring. Consider trying it and testing it against the springs in the DJ/FP kits which will be softer and allow the slide to open more quickly. A more quickly rising CV piston is not necessarily better. Having it rise too quickly will have you wanting for an accelerator pump. I am now of the opinion of keeping the air velocity up with a stock (stiffer) spring and letting the stock carb be what it is. It will never be a flatslide but if you "ride the carb" correctly they work fine.
To make jetting easier consider a kit that allows for a full airbox lid chop unless you are prepared to gradually remove material as part of the tuning process. Or get a stock lid. Some people have had luck with drilling the crap out of the lid.
Go with the biggest main jet you can get away with (a little on the rich side) and moderate needle positions. I wouldn't be the first guy to find that a little rich seems to work with the open airbox on the road, but the EGA on the dyno tells you to lean it off a little.
Don't get sucked into ruining a nice cruising mixture by over jetting the needle/midrange to make up for no accelerator pump. The CV carb with soft springs likes a roll on not a whack open for best performance unless you make the cruising mixture too rich. Again the stock springs will allow you to have a more forgiving carb.
Doug Lofgren is the only guy I know of that can get comparable peak power out of a CV carb similar to an FCR, but he blueprints them. I have it on good authority that he has passed on some tips to Brad over here in Oz, but I don't know if Brad has had time to work on it. The CV carbs are easier to synch and have an enrichening device ("choke").
The float levels are usually out from factory specs (so Ducati) and out from each other. Go for 14mm IIRC.
With a full airbox chop, if the kits are too lean, be open to stock 900 140 main jets, easy enough to get. However, I think the biggest main jets in the DJ kit will be a good starting point. The DJ kit will usually recommend a setting range for the airbox mod.
Someone who has tuned a 750 is bound to pop up with a good needle and main jet setting for an open airbox. If that happens then throw out my advice! ;D
Just a caveat, I have only played with the 900s. ;)
Nothing to add from me.
Great write up Koko.
i've got some stuff here at the start of this report: http://www.bikeboy.org/brads750m.html (http://www.bikeboy.org/brads750m.html)
*any and all other info or opinions is welcomed by all*
excellent writeups guys. Brad I peticularly liked yours as I read the entire thing. And being a nut when it comes to calculations and comparisons and actual specs, it was nice to see all the differences. I've been doing very similar things with import engines for years, accomplishing many things that most everyone said was never even possible. I've never done that type of thing with bikes before though, let alone ducati motors.
one thing I found very interesting was the difference in spring rates between stock and the factory pro springs, and mentioning the DJ springs were softer than the FP springs. I've watched the slides blipping the throttle off idle and was shocked at how much they shutter especially at such low rpm and fully understand what you mean by its more of a damping issue over spring rate issue. I always assumed the softer spring rates would allow the slides to open to a higher position at an earlier rpm, and guessed the kit springs would be softer specifically for this, never expected it to be that drastic of a difference in rate though.
I do tend to snap throttle often, so I'm assuming I'd be best using stock springs? only reason I was even considering a full kit so I could replace the springs is because of the stock springs being 12 years old and having over 20k miles on them. I'm thinking I might be best keeping the original springs though.
So I think it's safe to assume my best bet is to: keep a stock 42.5 pilot jet, adjust screws as necessary (currently at 4 turns out, may try 3.5), my current stock needles are 1 clip richer than stock but should try the DJ needles at the recommended 3rd notch, stock springs, and 135 mikuni main jet or DJ 148 main jet?
As mentioned in one of the writeups, street will show leaner at higher rpm/speed vs richer on the dyno; I imagine due to the slight ram air effect which I did foresee while comtemplating everything.
(I have not checked/adjusted float height yet, I'll make sure to do this soon)
for reference, below is my "mildly chopped" airbox as it currently sits. I opened it up enough to increase airflow, but not too much to have much of an effect on the ram air effect. the actual circle holes were cut out to the edge of the lips (~7mm larger radius increase) and obviously cut them down to tear drop shape to bring the holes further forward. I do not have a pad thing on the underside of my tank, in case that makes any difference.
(http://i62.photobucket.com/albums/h101/crluver123/IMAG0139.jpg)
also, I live in Connecticut. I've never done much work with bike carbs; what's the best/quickest place to buy individual mikuni and/or DJ jets from? I can't seem to find individual jets on ebay, or any standard bike store site
And the nearest ducati dealer is over 2 hours away
Quote from: motoxmann on July 29, 2012, 07:01:22 AM
also, I live in Connecticut. I've never done much work with bike carbs; what's the best/quickest place to buy individual mikuni and/or DJ jets from? I can't seem to find individual jets on ebay, or any standard bike store site
And the nearest ducati dealer is over 2 hours away
You might try Eric at clubhouse motorsports for Dyno jet jets. www.clubhousemotorsprts.com (//http://)
He used to be at BCM and they had a huge selection of Dyno-jet jets.
Mikuni jets are available from SUDCO. http://www.sudco.com/mikunijets.html (http://www.sudco.com/mikunijets.html)
I have some left over from my 900 kit if you find they'll work for you.
^thank you^
I dont know how old the jets in my carbs are. I've cleaned them best I can, but there is still some hazing/buildup on them that I dont want to attempt a rough cleaning of in fear of altering the flow patterns/rates of the jets. I would really like to get the most complete jet kit possible and/or brand new jets.
I still can't find any info on what's in the Factory Pro CRB-D08-1.1-TI kit
can anyone please identify, or provide a link that states, exactly what parts/jets and specifically what sizes are included in this kit?
Quote from: motoxmann on July 29, 2012, 08:31:10 AM
^thank you^
I dont know how old the jets in my carbs are. I've cleaned them best I can, but there is still some hazing/buildup on them that I dont want to attempt a rough cleaning of in fear of altering the flow patterns/rates of the jets. I would really like to get the most complete jet kit possible and/or brand new jets.
I still can't find any info on what's in the Factory Pro CRB-D08-1.1-TI kit
can anyone please identify, or provide a link that states, exactly what parts/jets and specifically what sizes are included in this kit?
Speeddog just put that kit in his 750.
He'll probably remember.
edit...
found this...
I have a Factory Pro Ducati Ti Pro carb kit for Monster 750's 97'-02'. Part # CRB-D08-1.1-TI.
Includes:
(2) Titanium needles
(2) Springs
(2) 42.5 pilot jets
(2) 45 pilot jets
(2) 135 main jets
(2) 137.5 main jets
(2) 140 main jets
(2) 142.5 main jets
Carb tuning guideline sheet
I have that Factory Pro kit on the desk right in front of me. There is only one set of pilot jets (#45). There are only three sets of main jets (no #135). Also includes replacement screws for the carb top and float bowls and several needle clips.
sweet, thanks guys. I'll have to open my carbs back up and see whats currently installed as well as check/set float height, and compare to what I think I'll need for size changes. I also emailed factory pro inquiring what's in their current kits, but being today is sunday I dont expect to hear back until at least tomorrow.
is it correct in what I've found that stock jetting is 42.5 pilot and 132.5 main?
AS DP said, I put the FP kit in my M750.
That list looks correct, I've got the info that comes with the kit at the shop, I can confirm.
floats at 14mm
#45 pilot jet
#135 main
FP springs
FP Nickel Plated Emulsion Tubes
needles on 2nd clip (counting from the top/leanest)
low speed fuel screw 1.25t out (for now, I've been occasionally fiddling with it for entertainment)
DP Slipons
Stock air filter
Stock airbox lid without snorkels
There's some relevant info I don't have.
I got this bike used.
There's at least two owners prior to when I got my hands on the bike, and it's had a hard life.
I suspect the motor is stock... but that's an assumption.
Cams, their timing, and internal engine mods are unknown.
Runs great, gets over 50 mpg with a 90% freeway commute.
In light of my low speed fuel screw setting, I'd probably put in 42.5 pilot jets if I pull the carbs out.
But given how well it runs, I'm not doing it just for that.
Get some main jet O-rings and float valve O-rings before you open the carbs up.
Given the vintage of the carbies, those usually are in pretty sad shape.
I recommend getting the FP Nickel Plated Emulsion Tubes, the OEM units oval out very quickly.
Thoroughly disassemble and clean the carbs.
A *complete* cleaning requires splitting the pair.
Be forewarned, getting the spring back into the throttle sync adjuster is a beyotch.
Watch for the O-rings:
On the vacuum port to the slide cover.
Under the plastic block that the slide runs on.
Also watch for the spring, washer and O-ring on the fuel screw.
Don't leave the slides sitting out for more than a day or two, I've seen the diaphragms shrink and then they're *really* hard to reinstall correctly.
Quote from: tbyte on July 29, 2012, 09:41:12 AM
I have that Factory Pro kit on the desk right in front of me. There is only one set of pilot jets (#45). There are only three sets of main jets (no #135). Also includes replacement screws for the carb top and float bowls and several needle clips.
is it possible someone used the 42.5's and 135's, and that's why they're missing? those seem to be the common sizes most people use
They are not listed on the invoice sheet that came with kit.
ok, so using the ducati microfiche and a few other resources, I've found that the stock jetting for the m750 is as follows:
pilot: size: 40, mikuni style: 151067
starter jet: size 70
main: size: 132.5, mikuni style: N208.099
so for starters I think I'll try the following:
nickel plated needle jets (emulsion tubes) from Factory Pro
DynoJet needles DNT729 directly from DynoJet (these are the ones included in their stage 1 and 2 kits)
mikuni jets from www.jetsrus.com (//http://)
2x pilots size 42.5
2x mains size 137.5
2x main jet o-rings
I'll be keeping the stock springs, as I tend to be jerky with the throttle and I think the DJ and FP springs will be too soft, and wont provide the positioning that I'll be after
and 14mm float height
reason I'll be only using the 42.5 pilot is because with the stock 40's currently installed, I'm at 4.0 turns out on the screws and its only a tad rich at idle and seemingly only a tad lean at light throttle and lower rpm cruise. I'm thinking only 1 size larger pilot will be enough, and will end up with a screw setting around 3.0. speeddog's post above saying he has 45 pilots installed and is at 1.25 turns out has me thinking 45's are definitely a hair too rich.
I'm following several different threads I've read on here, as well as the posts people have contributed in this thread in determining the DJ needles are probably better for what I'm looking for and what will work best with my setup, adn I definitely want more wear resistanct needle jets, and my personal preference is to stick with mikuni jets for the ease of comparison to stock and much higher availability
Sounds like a good start.
So I've been emailing with Marc from Factory Pro all afternoon/evening. He's been a bit dodgey in answering a few simple questions I've had, but generally has been very helpful and fairly quick to reply. I'm most likely going to use a full FP kit with a custom request of which jets to include. He doesnt know off the top of his head which jets are included in the standard kit, but will let me know tomorrow (monday) when he gets to the shop. He did say though generally 1 set of pilots and 3 sets of mains.
When I mentioned I may prefer stock springs over FP or other springs due to what was mentioned earlier, he noted: "As far as springs, there's reasons why we changed the springs. That's why we don't use stock springs." And then: " The dynojet springs don't have enough seat pressure. And that makes it soft at part throttle - If the bike is twitchy, it's usually too lean."
In the end, you can settle on your personal preference with spring/slow jet/needle pos-n combinations to suit yourself, tuning for the way the power comes on so to speak. I used to use the softest spring and a higher needle pos-n, now I would use a stiffer spring and a lower needle pos-n (or buy FCRs with accelerator pump) ;D.
You have done it with cars, so you will handle this better than most.[thumbsup]. It's just a process thing requiring alot of patience. In my mind, it's balancing the jetting requirements influenced by both the butterfly and the slide. There's two things going on at the same time. Flatslide carbs on the other hand have a more (relatively) linear process going on.
You may do some mods that allow you to access the carbs more readily like separating the airbox from the battery box.
Cheers.
Quote from: koko64 on July 30, 2012, 02:19:49 AMYou have done it with cars, so you will handle this better than most.[thumbsup].
haha thanks. yeah, I'm even considering welding an o2 bung to one of the muffler pipes just before the can (on the backside hidden) so I can install my wideband and datalog on the street. that'll at least give me a much better idea of what's going on. and if possible I may try to find a way to datalog rpms simultaneously. might have to buy an HT pickup clamp for a sparkplug wire. all tuning I've done with cars was efi, so I was able to tap right into the ecu for datalogging.
considering I have no clue how long ago the carb parts were last replaced, and the bike has 20k miles on it, I'm dying to see how much difference this all makes. because it does run quite well as it sits right now (besides a pickup coil needing to be replaced, and occasionally glitching causing minor loss of power)
I'm buying directly from FP, but in case anyone else is looking for a Factory Pro jet kit for their M750, I found the following ebay listing (they have 2 kits available in their ebay store):
http://www.ebay.com/itm/200775785079?ru=http%3A%2F%2Fwww.ebay.com%2Fsch%2Fi.html%3F_sacat%3D0%26_nkw%3D200775785079%26_rdc%3D1 (http://www.ebay.com/itm/200775785079?ru=http%3A%2F%2Fwww.ebay.com%2Fsch%2Fi.html%3F_sacat%3D0%26_nkw%3D200775785079%26_rdc%3D1)
I contacted the seller inquiring exactly which parts are included in this exact kit he is selling, and I got this reply:
Steve,
This kit includes:
2-PILOT JETS #42.5
2-PILOT JETS #45
2-NEEDLES
2-SLIDE SPRINGS
2-MAIN JET-#135
2-MAIN JET-#137.5
2-MAIN JET-#140
CARB SCREWS
Thanks,
Chris
Starcycle USA
800 990 2453
Quote from: motoxmann on July 30, 2012, 11:57:15 AM
haha thanks. yeah, I'm even considering welding an o2 bung to one of the muffler pipes just before the can (on the backside hidden) so I can install my wideband and datalog on the street. that'll at least give me a much better idea of what's going on. and if possible I may try to find a way to datalog rpms simultaneously. might have to buy an HT pickup clamp for a sparkplug wire. all tuning I've done with cars was efi, so I was able to tap right into the ecu for datalogging.
considering I have no clue how long ago the carb parts were last replaced, and the bike has 20k miles on it, I'm dying to see how much difference this all makes. because it does run quite well as it sits right now (besides a pickup coil needing to be replaced, and occasionally glitching causing minor loss of power)
The new needle jets will make a big difference.
The other stuff doesn't seem to wear too quickly.
Make sure you get some new main jet o-rings.
Quote from: ducpainter on July 30, 2012, 02:19:53 PM
Make sure you get some new main jet o-rings.
Yeah definitely will be, along with any other o-rings I come across while doing a full rebuild/cleaning, like the one between the jet holder and main body and such
Quote from: motoxmann on July 30, 2012, 02:37:32 PM
Yeah definitely will be, along with any other o-rings I come across while doing a full rebuild/cleaning, like the one between the jet holder and main body and such
Yamaha has a model that uses the same carbs. If you do a search it's been posted.
They sell a rebuild kit that might save you time and money over the individual pieces from Ducati.
Quote from: ducpainter on July 30, 2012, 03:15:00 PM
Yamaha has a model that uses the same carbs. If you do a search it's been posted.
They sell a rebuild kit that might save you time and money over the individual pieces from Ducati.
actually I have a hardware store right near my house that has a MASSIVE selection of o-rings, all of which are petroleum and heat safe. so thats covered haha. thank you though
Quote from: ducpainter on July 30, 2012, 02:19:53 PM
The new needle jets will make a big difference.
+1. I think FactoryPro suggest replacing them before rejetting if you've got more than 5k miles on them, 'cause that's enough to wear them sufficiently to make getting the rejet dialled in right.
FWIW (this is from decade-old memory), the FP jetkit I put in my 750 came with 135, 137.5, and 140 mains, and 42.5 pilots (and new FP taper needles). After a few rounds of rejet/dyno-runs, I ended up with the original 132.5 mains with the new needles on the second-from-top (leanest) groove and the 42.5 pilots - and a pretty much _perfect_ air/fuel ratio right across the rev range for 100%, 50%, and 10% throttle runs. That was with Staintune slipons on stock headers, and a severely chopped airbox lid (just enough to keep rain out) and a K&N filter. It took a while (and cost a bit), but I was very happy with the outcome.
big
good to know, thank you
I read an old post and had had some Duc CV carb spring rate input.
...................
The "stock" CV carb springs are a "thick wire, many coil" spring.
In my experience and opinion,
The stock springs have the same 2 problems as the DJ "thin wire / few coils" spring. Just a bit less in intensity.
...................
The DJ carb springs have less "seat pressure" than stock and that overrichens the part throttle / high rpm operation.
and
I couldn't get the WOT / low rpm to run lean enough to pass my R&D tests - the slides lifted too high and exposed the point of origination of taper on the needle. The DJ and stock spring mid lift "pressure" was too soft.
Those are "my" tests and how I think how a carb should supply fuel to a Duc.
...................
The Factory Pro springs have somewhat more "seat pressure" than stock springs and def more seat pressure than the DJ springs - That's why, with the FP springs, when you are at 5k / neutral throttle and getting ready to feed the throttle on, the FP springs (because they are not making things overrich) provide crisper power at small throttle openings.
I like that feeling.
The FP springs have a higher midlift pressure and that allows tuneable full throttle / low rpm - getting away from the "too rich" at full throttle / low rpm feature of the DJ and stock.
...................
A feature of the DJ springs is that WOT at low rpm in 1st gear will produce soft power (full throttle) at lower rpm, but then a harder "hit" at higher rpm. I don't care for that as the tradeoff is softer power at lower rpm - both at full and part throttle.
The FP spring pulls harder and cleaner at full throttle / low rpm but doesn't do the wild wheelie at high rpm in 1st, like the DJ springs.
The FP spring, at 4k / cruise, when snapped from neutral throttle to 1/2 throttle, is likely to pull the front wheel up (controllably). The DJ spring doesn't do that. Very noticeable.
I've resigned myself to the fact that I can't please everybody :)
Some people like the DJ spring feel and some people like the FP spring feel.
And then there's slide damping holes.........
Personal preference and "feel" make for interesting tuning for different customers. We're a pernicketty bunch. [laugh] But seriously personal preference is important, but hard to cater for somtimes. Anyway, they're bloody CV carbs. [laugh]
I suppose a range of springs available, like a range of jets would just add cost and headaches when making a kit.
I tuned some FCR 41s for a guy on an M900. He chose the jetting option that I thought gave the shittiest power characteristic. Go figure.
Then there's "preloading" slide springs on old Delortos and Amals [bang].
I tried both the DJ and the FP springs shortly after this thread was in action, and I must say the DJ springs do pull a little harder up top, but low and mid rpm were pretty crappy and frankly annoyed me quite a bit. then again, the top end may have only FELT more powerful due to the low/mid suffering so much.
the FP springs are MUCH smoother throughout the entire rpm range, and give quite a bit more torque in low and mid.
the issue with the DJ springs I'm sure is simply from the springs being too low of a rate; they open too early, and too far, at all points, which decreases velocity and makes the slides shudder too much, also making fuel delivery inconsistent and "globby"
+1
A pretty fair description imo.
What set up are you going to settle on?
Quote from: koko64 on November 01, 2012, 06:26:43 PM
+1
A pretty fair description imo.
What set up are you going to settle on?
FP springs, FP nickel plated needle jets, FP needles.
I actually like the DJ needles a little better, only a hair better, visually and functionality [when used with the fp springs]. but after only 500 miles [combined with new FP nickel plated needle jets] the DJ needles actually showed signs of wearing!! EEK! enough so that I knew the profile wouldnt mean squat after long. so the FP needles went in. the difference in performance IMO between the FP and DJ needles was very very difficult to tell, but ever so slightly noticeable. both were way better than stock though. and I now have 2500 miles on the FP needles, 3k on the FP nickel plated needle jets, and zero signs of wear on anything, so I'm very happy :)
from my calculations, the original springs are 92N/m, factory pro 29, dynojet 21 and original 400ss/m springs 37. the lengths follow that sequence too, from shortest to longest: original, dj, fp, 400.
compressed to 70mm, the original have 2 N load, the dj 0.5, the fp 1 and the 400 2. with the slides fully open (another 35mm compression) it's 5.5, 1.5, 2 and 3.5