Ok, as I re-work my M750, it's in dire need of needle jets. I'm going to pick them up from CA Cycleworks. However, I see he also has a 37.5 pilot listed. That got me thinking. I'm running stock airbox, w/ snorkels, and Termignoni mufflers w/ wrapped core.
Any need to fiddle with main jet size or anything like that? I've not been in the carbs, so I'm assuming they're stock. She was running pretty rich, only getting about 35mpg.
I'm also planning on pulling the hose that goes from the airbox to the canister and to the crankcase vent. I'll stick a little filter thingy to replace the hose.
Suggestions?
JM
I wouldn't change anything but the needle jets unless you were planning on opening up the airbox and doing a jet kit.
Worn needle jets will kill mileage.
+1
Consider Factory Pro stainless steel needle jets (if they still make them). They should give good wear with your stock needles which are fat enough to not wriggle around too much and contibute to wear.
Factory Pro say a 14mm float level should be used. I think the Ducati Suite site and FP sites cover how to do this. The float levels are often out from the factory. A search for DMF threads about this should also bring something up.
When the carbs are apart, the obligatory clean with carb cleaner, there's often a lot of gum, dirt and varnish deposits.
Oh, and watch out for the little o-ring under the carb top that wants to hide when you take the top off! The little buggers.
Cheers
Change the float valve O-rings while you're in there.
Quote from: Speeddog on January 17, 2011, 02:14:54 PM
Change the float valve O-rings while you're in there.
...and also the ones on the mains while you have them out to replace the needle jets.
Where do I find/order those o-rings from? I'm sure one of our sponsors carry them.
JM
Cal Cycleworks sells them. I guess some dealers would have them also.
So, I'll need this:
http://www.ca-cycleworks.com/factory-pro-needle-jets-sold-each (http://www.ca-cycleworks.com/factory-pro-needle-jets-sold-each)
and this:
http://www.ca-cycleworks.com/ca-cycleworks-this-is-the-scarce-main-jet-o-ring-for-ducati-mikuni-cv-carbs-sold-each-recommended-to-be-purchased-with-jet-kits-factory-brand-jet-kits (http://www.ca-cycleworks.com/ca-cycleworks-this-is-the-scarce-main-jet-o-ring-for-ducati-mikuni-cv-carbs-sold-each-recommended-to-be-purchased-with-jet-kits-factory-brand-jet-kits)
Ca doesn't carry the float valve o-ring.
JM
Did you remove the float valve?
How's that carb rebuild going?
Quote from: ducpainter on March 06, 2011, 02:12:15 PM
Did you remove the float valve?
No, I've not even pulled the carbs off yet. That will happen this coming week. Really, I just plan on opening the carbs swapping the needle jet and required parts and putting it back together. The bike is mostly stock. It's got Termignoni mufflers instead of stock, and the air filter has been swapped to a oiled-element type. I think it's BCM maybe. It is not a K & N.
Quote from: koko64 on March 06, 2011, 02:51:09 PM
How's that carb rebuild going?
As of yet, it's not even started. Been doing a bunch of other stuff first.
JM
Quote from: the_Journeyman on March 06, 2011, 03:28:38 PM
No, I've not even pulled the carbs off yet. That will happen this coming week. Really, I just plan on opening the carbs swapping the needle jet and required parts and putting it back together. The bike is mostly stock. It's got Termignoni mufflers instead of stock, and the air filter has been swapped to a oiled-element type. I think it's BCM maybe. It is not a K & N.
As of yet, it's not even started. Been doing a bunch of other stuff first.
JM
You should replace the main jet o-rings as they are known to crack when they're pulled out of the emulsion tube.
I wouldn't worry about the float valve o-ring.
It's probably a BMC filter.
Sounds good. Gonna go place an order with Ca-Cycleworks. I'm looking forward to this thing running like it should, without hesitation when I roll on the throttle!
JM
Ok. Emulsion tubes are here along with new main jet o-rings. I've never been in the carbs for a Duc before. Are there any surprises I'm going to encounter? Seems fairly simple, but I can't see the emulsification tube on the parts fiche. I know where it should be, so finding it shouldn't be a problem I'm thinking.
JM
Easiest explanation is the main jet pushes into it.
Remove the retainer for the jet remove the jet, and then push the needle jet/emulsion tube up towards the slide. You have to remove the vacuum diaphragm/slide to change the tube.
Thanks dp, I'll give it a shot!
JM
Ok, so after spending the day draining fuel, removing tank, removing airbox (this requires the battery to come out, the coil rack to be removed from the airbox, and then the ignition switch removed to allow the airbox to slide free) as well as various electrical connectors and a few wires.
Removing the carbs completely from the bike requires disconnecting the fuel line, both throttle cables, choke cable, and the various vent lines. Ducpainter mentioned it didn't remove the carbs for changing the emulsification tubes, and next time, I won't either. You can get to everything with them on the bike, just work around the frame tubes and I'll probably move the oil cooler out of the way.
The carbs themselves are reasonably simple. I did find a T-handle phillips head driver was very handy for removing the very tight bowl screws. Once the bowl was off, I removed the diaphragm & slide. Emulsification tube just pushes up through the carb and out. Slide the other in, line up properly with the main & pilot carrier and you're good to go. Put retainer back on and reassemble.
Compare the two tubes:
Old on left, new on right.
(http://i304.photobucket.com/albums/nn168/the_journeyman/Molly/Tubes.jpg)
Now, off to source diaphragms since mine have cracks. I'm very interested to see how she'll run with good emulsification tubes and not cracked diaphragms.
JM
I had that work done at the dealership on my 2000 750 last fall and the results were great. Mileage is back up to 48 - 53. The bike sounds better, responds better. I think you will be pretty happy. Not enough guts or smarts to dig into the carbs yet on my own.
Quote from: WarrenJ on March 13, 2011, 06:57:01 PM
Not enough guts or smarts to dig into the carbs yet on my own.
Go for it. It's really a lot more simple than most people think. Took me a year to build up the courage due to the many horror stories i'd heard. But once in, no sweat at all.
Fine tuning the mixture and balancing is more of a challenge but still well worth the effort.
I studied up on the valves and that went pretty smooth so next time, I'll dig into the carburation.
Yea the carbs themselves are relatively simple. All the stuff you have to work around to get to them is more frustrating than the carbs. These are the most modern carbs I've work on, and I didn't find them very difficult to work with.
JM
Quote from: the_Journeyman on March 11, 2011, 05:04:14 PM
Ok. Emulsion tubes .
Journeyman...I am doing this exact same thing this weekend and wanted to get a head start on cleaning and tore one of the O-Rings...where did you purchase the emulsion tubes ? I bought my gear from CA but did not see those specific items...Bought the
Factory Pro titanium kit
Pilot Jet for Mikuni CV Carbs, #37.5
scarce main jet o-ring
The tubes I bought came from Ca-Cycle works, they also supplied the main jet o-rings. My mains refused to budge, so I didn't bother using my main jet o-rings. I'm using the stainless Factory Pro tubes with the stock needles. I also had to replace my vacuum diaphragms.
Which o-ring are you referring to? There are several in the carb.
JM
I tore the o-ring on the main jet. I am waiting on those to arrive from CA. But I did not see the tubes on the site.
Quote from: MaaloX on March 17, 2011, 02:33:46 PM
I tore the o-ring on the main jet. I am waiting on those to arrive from CA. But I did not see the tubes on the site.
They sell factory-pro and the tubes are available separately from them. Maybe call Chris and ask.
If you search for "needle jet" on CA's site, you'll find them.
JM
Everything is back together. Starts easily but doesn't want to come on the throttle. You can see the slides hopping up and down as you try to increase the RPMs. In the first video, she chokes out and dies.
New emulsification tubes, new diaphragms too. Everything else in the carbs looked good.
In this vid, it chokes and dies when I get on the throttle, but you see the slides kind of hopping up and down as it attempts to throttle up
0320111911a.3g2 (http://www.youtube.com/watch?v=lcCIiJ02iO8#normal)
In this vid, around 0:14 you see what happens really well.
M750 with fueling issue (http://www.youtube.com/watch?v=WFKseq0sku8#normal)
JM
How old is the fuel?
Couple months. However, turns out not the be the fuel.
Total dumbass move on reassembly. Turns out, while I had the diaphragm cap off the right hand side carb I had a dumb. When I put the cap back on, I managed to catch the choke cable between the cap & carb both. Totally killing my vacuum. Responds very nicely now. I'll take another test ride tomorrow and see on the road, but it was way better in the garage.
JM
Jetting is the combustible devil.
So... Good response mid-high RPMs. Just off idle, not so much. Sputtering, won't take throttle, killed it a couple times by just twisting the throttle from idle. Not sure if it's rich or lean. Less engine braking at low RPMs, like almost non-existent, popping if I barely open the the throttle. Very unstable at small throttle openings, if I try to maintain a small throttle opening, it is very choppy.
I'm leaning rich, even though I think it was a 70 in the pilot spot. I say rich, because after shutting motor off when warmed up, I can just barely tap the starter and it's idling again. Idles ok, sometimes really low, sometimes hangs a bit on closing the throttle.
I suspect the pilot, because once I really open the throttle, everything is fine. Mid to full throttle it responds fine.
JM
Size 70 is usually for the starter/enrichener jet (big flat head one holding the main jet retainer plate/clip. The Pilot jet should be around size 40 for a stocker (some models have a 42.5 and there are 37.5 available). If it's stinky rich you can check your float levels or check that your enrichener/choke cable isn't too tight.
If it's still too rich after those things checking out you may have to reconsider the needle height if it's adjustable and your idle mixture screw adjustment. Needle adjustment notches are counted from the top notch (leanest).
Check that there is no fuel overflow from the carbs overflow hoses. You will see fuel dripping out of the hoses with the bike idling. If there is, you will have to clean out the float bowls and float needles/seats. Some people tap the float bowls with the back of a screwdriver to seat them like smacking an annoying toilet sistern. Some remove the drain plugs and let fuel flow into a recepticle held under the carbs to flush fresh fuel over the faces of the float needles to clean them. These are the dodgy and bodgy ways to clean your carb float needles without pulling them apart. It has worked for me, just do it with a cold engine in case you spill fuel.
This is assuming it's running rich. Black plugs will confirm this.
Well, here's the breakdown of what I found.
I have 1 black (rear) plug and one whitish plug (front) and once she gets good and warm, everything but the 1/8th or so throttle opening stutter goes away. I'm going to try to lean up the fuel screw on the rear a half-turn and see what happens.
JM
Well, I've smoothed things out for steady-throttle with the fuel screw adjustment. Got the idle about right, it's just a "it sounds good" verification since I have no tach.
Lets review: OEM jets, 14mm (best I can tell, not good at measuring it) float level, fresh emulsification tubes. Sync? Haven't done it, don't have the stuff to do it.
Starting: Choke, thumb starter, maybe a slight twist on the throttle and she roars right to life. Once idle starts to drop, push choke back about half-way, after another minute or so, cut off choke entirely. Idle is a little lumpy, but smoothes out as engine warms up.
Taking off from a stop = stumble, chug, bog etc, but then throttles on up if I hold the throttle open.
Mid throttle - Fine & snappy, plenty of go.
Full throttle - Still ok, but a tad off, not sure if lean or rich yet, but the neighbors are all coming out the see what the hell I am doing. Maybe a hair lean since it surges slightly as I ease off throttle
Engine braking is normal at higher RPMs, but seems very light at lower RPMs.
I STILL have the bogging/chugging/hesitation when first opening the throttle. It is MORE evident if I am loading the engine (releasing the clutch to take off) than if it is just sitting idling and a twist the throttle.
What would shimming my needles with a thin washer achieve? If I am lean causing the off-idle bogging, I seem to think it would help. If I'm slightly lean higher up, the needle would be slightly richer throughout it's travel, and might fix that full throttle surge on throttle close, I think.
More experienced folks, what do you think?
I think you need to synch the carbs before you try to make small fueling adjustments to correct a problem that might not really exist.
I don't have any type of vacuum gauge. Is there any other way for checking the sync?
Plug ends are grayish-white if that is worth noting.
JM
Quote from: the_Journeyman on April 20, 2011, 06:27:33 AM
I don't have any type of vacuum gauge. Is there any other way for checking the sync?
Plug ends are grayish-white if that is worth noting.
JM
You can make a tool for like $10. You will need a way to connect to the manifolds via the 5mm plugs.
Google 'homemade carb synch tool'
I'll check that out and see. I also had a local wrench guy tell me about a mechanical sync method that used feeler gauges & the butterfly valves. He had done it several times & checked it with a vacuum gauges and it had balanced them properly.
Basically you run the idle speed all the way down, put the feeler gauge in the master carb, compare with the secondary, adjust until they match. It's purely mechanical, and it seems there are lots of other variables that could affect it, but at the same time, it might work.
JM
Quote from: the_Journeyman on April 20, 2011, 07:03:14 AM
I'll check that out and see. I also had a local wrench guy tell me about a mechanical sync method that used feeler gauges & the butterfly valves. He had done it several times & checked it with a vacuum gauges and it had balanced them properly.
Basically you run the idle speed all the way down, put the feeler gauge in the master carb, compare with the secondary, adjust until they match. It's purely mechanical, and it seems there are lots of other variables that could affect it, but at the same time, it might work.
JM
That was the way we did it back in the day with multiple cyls and separate cables for each carb. Those were slide operated carbs though
It's better than nothing, but may not solve your problem because of the vacuum pistons in the carbs.
Small differences in cylinder condition will affect vacuum and overall mixture.
I'll try it and report back. If it doesn't improve things, I'll make a vacuum gauge. He did mention that if there were major difference in leakdown it wouldn't work as well.
Speaking of the 5mm nipples. It seems mine are simply connected to each other by two hoses that are clamped together in the middle. Is that normal? Seems a cap on either side would be just as good and less prone for leaks.
JM
Quote from: the_Journeyman on April 20, 2011, 07:36:33 AM
I'll try it and report back. If it doesn't improve things, I'll make a vacuum gauge. He did mention that if there were major difference in leakdown it wouldn't work as well.
Speaking of the 5mm nipples. It seems mine are simply connected to each other by two hoses that are clamped together in the middle. Is that normal? Seems a cap on either side would be just as good and less prone for leaks.
JM
That's how whoever did the canister removal did it.
You can use the two hoses for fogging if you store the bike, or you can use caps. Either way works.
Good to know about the hoses.
The feeler gauge method doesn't seem to work with the carbs on the Monster. I can't get a feeler gauge between the carb bore & the butterfly valve. Off to look up vacuum gauges ~
JM
I used this tutorial to make my sync tool...
http://www.daraq.com/Bike/10dollar_carb_sync.pdf (http://www.daraq.com/Bike/10dollar_carb_sync.pdf)
I ended up using these for the bottles as I needed a pick-me-up that day :p
http://www.starbucks.com/menu/drinks/bottled-drinks/bottled-frappuccino-vanilla?foodZone=9999 (http://www.starbucks.com/menu/drinks/bottled-drinks/bottled-frappuccino-vanilla?foodZone=9999)
I've used my 2bottle kit to sync my 4 cylinder yamaha. It really is very easy and cheap to make and very reliable as long as you dont destroy your rubber stoppers like I did the first time. Putting the hole int he rubber is easier if they are cold. But not frozen. Frozen can make them crack (ask me how I know).
Also, I didn't use water. I used mixed 2stroke fuel. I've heard people use heavier liquids like ATF or the like as well.
So, after looking around at my local stores, I could find everything but stoppers. So, I found a vacuum gauge for $20 at my local auto parts.
My findings:
Both carbs at idle pull 7lbs of vacuum.
Next issue. As soon as I open the throttle - Vacuum is GONE. Same on both carbs. Am I doing something wrong? Or is it supposed to loose all vacuum when you open the throttle.
I notice once I coax it into revving up, vacuum comes back but only in a small amount until I close or even back off the throttle it runs up to between 10 & 15 pounds of vacuum and drops as the RPMs drop back to idle.
I just opened the carbs back up, and my pilot jets are clear too. I'm completely stuck at this point. It ran fine before I put new emulsification tubes in.
JM
Success!!! Finally.
One carb was rich on idle mixture.
It seems there was a bit of a learning curve to using the vacuum tool. I found a slight difference and adjusted it out.
Thanks everybody for all of the help!!!
JM
Quote from: the_Journeyman on April 20, 2011, 03:21:17 PM
Success!!! Finally.
One carb was rich on idle mixture.
It seems there was a bit of a learning curve to using the vacuum tool. I found a slight difference and adjusted it out.
Thanks everybody for all of the help!!!
JM
Imagine...
learning. ;D
Yea, I learned a whole lot about carbs this week. I also learned that once I get used to the method, I can have the airbox removed in short order. I've learned where all of the screws that affect how the carbs operate are and how to used them. I'm still a little pissed at the previous owner for stripping the head on the front carb idle screw.
JM
Rise from the dead!
I recently disassembled my carbs because of this thread and found that the PO installed a jet kit. What seems odd though is that the needles are set at two different heights (3rd slot and 4th slot from bottom)
Is this normal or should they both be set in the same slot?
Also, the float bowl screws got trashed as I though I would be installing a jet kit. Now that I don't need to, I can just replace these screws. Anyone have the size offhand?
Quote from: Dellikose on January 09, 2012, 01:39:02 PM
Rise from the dead!
I recently disassembled my carbs because of this thread and found that the PO installed a jet kit. What seems odd though is that the needles are set at two different heights (3rd slot and 4th slot from bottom)
Is this normal or should they both be set in the same slot?
Also, the float bowl screws got trashed as I though I would be installing a jet kit. Now that I don't need to, I can just replace these screws. Anyone have the size offhand?
Typically the needles are set the same. A tuner might have raised the vertical cyl a notch.
The screws almost always get trashed. Factory Pro includes screws in their kit. They are available at most hardware stores, or auto parts stores. 3 or 4mm.