A few questions on VM29 carbs

[KEITH KRAUSE]

Ok. Sounds like almost a catch 22 situation.
You say you needed to lean the needle a bit, but now the pilot circuit may be too lean. I hate the overlap effect. The jet needle effects minimal throttle positions more than some people realize. It even varies a bit, bike to bike, depending on mod's. Try some air screw adjustments as you said, and let me know what happens. But if the screws have to be nearly seated to get results, that would sound like compensation jetting to me. I don't get much chance to "play" with the 29's, so I appreciate the back and forth and chance to learn. Might help someone else down the road.
I hope the cut-away you have isn't causing the problem. The cut-away is for the transition from pilot jet to needle jet/jet needle. But another member here recently said he has 2.0 cut-aways and it runs good. Now you say leaning the needle is causing pilot circuit problems.
I think the solution may be to put the needle at 2 1/2 position, by using a jetting spacer. If indeed position 3 is a little too rich, and position 2 a little lean, then you could put the needle's e-clip back to 3 and place a .022" thick jetting spacer on top the e-clip.
PS: just reading back briefly, on the 31st, you said you had a feeling the bike was rich when the needle was at position 3, correct? You didn't sound real positive about it. You said the plugs were dark after just riding around normally? I wonder if the jet needle position or the pilot jet was to blame for those "dark" reads? You never came back with a definite plug read after a 1/3 throttle test with the needles at 3. You just came back that you changed the needles to position 2. To tell you the truth, the jet needle being at position 2 (second from the top) seems lean. Just thinking out loud here.

[Rock]

I reset the air screws and synced again. The screws are from 3/4 to 1/2 turn out now, on average about 1/4 turn in on each screw made it right. The popping is gone and she is running strong. I have yet to do another plug test. I'll probably do it tomarrow. I hope it's reading good now. If not I guess I will have to richen the needle some like you suggested and may have to live with the results? I don't believe going to a bigger pilot would help as I would be right back to where we started from with all the jets and far to rich at low speeds. From what has happened so far and with my limited experiance I think the pilot is the right one. I am sure I did a plug read again (?) after after changing the pilot and failed to mention it. With all the changing around I am trying not to miss any steps in the order to tune it. I too hope it isn't the cutouts because they are really expensive. I think (hope) we'll have it now, I have enough practice with the sync gauges now. I really appreciate all the help and maybe it will help someone else down the road too. I know I'm learning a lot.

[KEITH KRAUSE]

Let us know what happens. I hate to sound negative, but the air screws being adjusted so far in reminds me of what I call compensation jetting, which is making an adjustment that seems odd but because another adjustment is off, the two "cancel" each other out and the bike seems to run good. But usually you'll notice problems before long, such as poor gas mileage, loading up while idling, stalling after hard acceleration when hot...all this is from a rich pilot circuit of course (assuming carbs are clean and floats set correctly.)
On VM carbs, the air screws should be set for maximum idle rpm. Same as we used to do on cars with carburetors. You always set for highest rpm and leave them alone. Any needed changes to the jetting would have to be done with another component, because the correct way to set the air screws is by the highest rpm method. Adjusting them so far in is just incorrect. I know this isn't what you want to hear.
And let me say again, I don't have a lot of experience with the 29's, but they should follow the same procedure as other carbs with AIR screws.
It seems with your set up, the jet needle kicks in very soon. Then there's the cut-away question, and the accelerator pump factors in too. Really has me scratching my head.
If you decide to keep adjusting the jetting, it seems to make sense to raise the needle 1/2 position, then adjust the air screw for highest rpm and re-test. It's a little confusing trying to go back and piece together what all's been done and the results. If you kept records of every single adjustment and the result, I'd like to see it. I keep records of every re-jet and it really helps to make sense of things. I write down every adjustment, what happened to performance, and plug color.
I hope I'm not causing confusion. Jetting can be frustrating I know. I just feel I should say what's on my mind though, right or wrong.
You did replace the manifold o-rings and check the manifolds condition? Does the accelerator pump appear to be operating right? Choke plungers operating right and closing completely just before the thumb lever is completely off?

[Rock]

I took the bike for a ride last night and just wanted to see how it ran. I got the chance to do a 1/3 throttle test because of the unexpected lack of traffic. I only checked the two outside cylinders because I only had my factory tool kit with me and it's hard to do the inner plugs with that set up. Both plugs showed good.

I did adjust the air screws to the highest rpm. I spent some time at it and went through them a few times in different order to ensure settings were dead on. Before this last test with the same jetting I did adjust for highest rpm also but adjusted them out to the furthest point before the rpm started to drop off again instead of using the furthest in position at the highest rpm as recommended by Mikuni. This resulted in about 1/4 turn or so on the screws, the sweet spot was that big and did not change the rpm. I was trying to keep it on the leaner side which I found caused the popping.

The history so far, basically I started out with the carb as I got it on the bike and it was already jetted by Mikuni specifically for this bike according to Sudco's information. I didn't write the changes down so this is from memory the best I recall. I will write all the changes so far and keep records, I should have done that from the start I guess to lessen the confusion. I confuse myself sometimes the way I write. I first tried to adjust air screws with the original pilot #25. It just burned too rich and would smoke some at idle also. I then went to the 20 pilot and tried that. I did not do a low speed test at this point. While just riding around at combination highway and city would soot the plugs pretty bad. I know it didn't work out for riding around. I then lowered the needle one notch and still have the #20 pilot installed. It's now two from the top, or one above the center. I know what your saying about the air srews being so far in but it appears at this point to work so far. I'm going to go to the other thread where the guy has #2.0 cutouts too and see if he knows where his air screws are at. I have to say it ran excellent last night, starts right up, was powerful, smooth running and really purred at idle. Checking all the plugs today at 1/3 should tell us more. I'll do a low speed test also.

I did not replace the manifold o-rings but did spray around them and check for leaks. The manifolds are plenty pliable and in like new in apppearance. Do you think I should go ahead and change the o-rings out anyhow? I planned to eventually anyhow but though I'd wait until winter. I did put a new diaphram in for the accelerator pump also. You won't hurt my feelings asking any questions about the steps I've taken so far. The most I have ever had to do with a carb on any other bike I owned was adjust the idle and a mix screw

[KEITH KRAUSE]

When I make suggestions, like changing the manifold o-rings, it's because it's an automatic part of a re-jet TO ME. I make sure all the parts are right so any problems are truly the fault of the jetting components. I know it's more work though. If you still have the stock Phillips screws in the manifolds, they can be a pain to remove. I replace them with Allens and torque to 6 ft/lb. Apply some hi-temp' bearing grease to the o-rings to help them last.
The classic symptom of an intake leak is the bike will idle at say, 1,100 rpm's at start up, but the idle will climb significantly as the motor warms up fully. You haven't mentioned anything like that but I still always change the o-rings unless I know the bike and I'm positive they're still good. They're cheap. It's just the potential trouble with the stock screws that can make the job any trouble. Use an impact tool with a GOOD FITTING bit.
Let us know how the bike runs and if they're any issues after you put some all around miles on her.

[Rock]

Kieth, I have not found any jet spacers yet to try the 2 1/2 position on the needle as you suggested. So just to check again I went back to the middle #3 position from the #2 on the needle and did not change the #20 pilot. Well there must be some overlap as you said. I adjusted and synced again and the plug tests showed rich at low speed test. The plugs were acceptable but not all actually tan at the 1/3 throttle test. One was a touch rich. I did not change the pilot, it is still the 20 and the plugs were not nearly as clean either as the previous setting at the #2 on the needle with the #20 pilot. That change of on needle position back to #3 really threw things out of whack and did have a big effect on the pilot circuit. It still runs good but is rich with a slight puff when I flip the throttle at idle. The plugs are quite dark on the low speed test now. I am going to go ahead and put in new o-rings and recheck valve adjustment also.

I am somewhat confused now as to what is the best plug color. I have seen on the web any where from wanting to be tan to others saying a ash color. BEFORE I dropped the needle back down from the #2 position to #3 today I had light tan to ash colored plugs at 1/3 throttle and decent tan reads at low speed. Do you feel grey ash color (not white) is a good indicator or is it going to be a bit lean at that? If those reads are good I would say that is the best combo of jet setting I have had.

I guess I need to find some jet spacers and try 2 1/2 on the needle and maybe I would get a tan plug read with the #20 pilots. About the only combo I haven't tried with my jets are to reinstall the #25's that were on when I started this project and the drop the needle back to #2 position. I never tried that because the pilot system seems to be the problem and the needles were originally at #3 position. I don't know if that makes any sense, but changing the needle with the #20 pilot made quite a change in the pilot circuit low speed test. You also once mentioned going down one more pilot size also which to me seems like that would be right seeing as how the pilot circuit is rich and seems to be the problem. But wouldn't that in theory result in me closing the air screws even more as less gas is flowing at low idle through the pilots, or is that thinking wrong? Mikuni (not much help) manual says if you have smoke the pilot is too big and if it runs irregular at low speeds the pilots are to small. But will a pilot also affect 1/3 throttle speed to some extent too? I know the needle had a big effect on the pilot circuit.

I guess I'm looking for perfection and maybe I won't find it unless those ash plugs are good. Another thing, when I'm at 1/3 throttle the bike is doing about 85 mph. Would that really still be the needle circuit? I have to get off here, I'm starting to even confuse myself.

[KEITH KRAUSE]

Hi. I just read your message but I'm just leaving for work.
As two quick thoughts, I might try the needle position as it is (3) with a 17.5 pilot jet and air screw adjustments. OR, Get a jetting spacer to put the needle at 2 1/2 and re-test. If one of those combo's don't work, I have to guess the cut-away is factoring into the problem??
If I can I'll try to give some more ideas/info tonight.

[Rock]

I'll see if I can get some 17.5 pilots today. It just seems odd I have to change the jetting so much when the previous owner said it worked great as is. He had it tuned by a performance shop from what I was told. On the other hand I guess that doesn't mean it was right either. Any thoughts on the plug reads as far as ash color versus tan?

edited to add, I just found a post about the VM29's on another forum and it was stated the air screws are at 1/2 turn out on the 29's and 1 1/2 on stock carbs. Maybe the position of my air screws is not abnormal for the VM29's. Of course that info could be wrong but it sounds like at least one other guy has them set inside one turn. They were turned in pretty close to closed when I got the bike also. You can see the shiny surface on the screws if you back them out much past my setting which indicates they were always adjusted in. Also another thought, when I set my float height the weight of it does compress the needle valve somewhat. Should this happen or are the springs weak in the assembly weak? The seats and valves are in great shape.

[jeff.saunders]

1/2 a turn out is way too little on those carbs. As Keith said - it's trying to overcompensate for a wrong pilot jet. All the VM29's I've worked on end up with the airscrew being between 1 1/4 and 1 3/4. If you need larger pilots we do sell them (and stock a fair number of parts for the VM29's).

http://www.z1enterprises.com/catalog.aspx?pid=KPCF3

One other thought is to make sure the holes in the ends of the airscrews are clear - these can get clogged - also they can get damaged by seating them too hard before backing them out...

[jeff.saunders]

When Mikuni first started selling the VM29's, they came with 120 main jets and 17.5 pilot jets. Then as larger capacity bikes and more radical setups started to be common, Mikuni gradually bumped the pilots from 17.5 to 20.0 all the way up to 25.0 in the last generation of VM29's sold.

When VM29's were sold for GS applications, Mikuni ALWAYS recommended 2.0 slides for the 750's and 1000's - I can't tell you why, but even the original documentation from the late 70's states this. I can tell you 2.0 slides are leaner and do requirer a larger pilot to compensate.

Keith, I'd like to understand why the 2.0's don't work on the GS750's & 1000's - I don't have much experience with the VM29's on GS's (mainly on Z1's) - so your comments would be useful.

BY the way, Mikuni recommended 1.5 slides if used on the GS550

[Rock]

1/2 a turn out is way too little on those carbs. As Keith said - it's trying to overcompensate for a wrong pilot jet. All the VM29's I've worked on end up with the airscrew being between 1 1/4 and 1 3/4. If you need larger pilots we do sell them (and stock a fair number of parts for the VM29's).

http://www.z1enterprises.com/catalog.aspx?pid=KPCF3

One other thought is to make sure the holes in the ends of the airscrews are clear - these can get clogged - also they can get damaged by seating them too hard before backing them out...

Jeff, I started with the #25 pilot as it was in the bike when I got it. It was way to rich and would smoke some at idle. I have tried the #20 and while it is a bit better it still is somewhat rich. I then dropped the needle down to the 2nd notch with the #20 and the plugs were very light tan to a grey ash color. I have always adjusted the screws to the highest idle and with the #20's they end up at 3/4 to 1/2 turn. I haven't tried the#25 pilot and the 2nd notch on the needle. I did check the air screws for blockage and will do so again to double check them. Any ideas you could give would also be appreciated.

By the way I ordered a accelerator pump diaphram from you a few weeks back that was for the Kawasaki VM29. I talked to either you or someone else there and got the measurements before I ordered it, yes it did fit. Nice site. The previous owner could never find one. Thanks

[KEITH KRAUSE]

Jeff, other than what I've said in this topic, I really don't have any facts about the "standard" cut away size for the 1000's. You seem to have more experience than me regarding their use. I certainly wouldn't argue with you. I let Rock know from the beginning that my past experiences were that the standard cut away was 1.5, and it was my assumption this was normal.
If I'm wrong, at least it hasn't caused him to run out and buy parts.
We're all learning from each other here. You did bring up something that has me very embarrassed and my next post will mention that.

[KEITH KRAUSE]

Rock, about the cut away size and how it effects the mixture.
I don't know how I reversed it when I posted, but the larger the cut away, the LEANER the mixture. I told you the mixture would be richer. Jeff mentioned that and I stared at it for a second and just said "nooo..." I certainly know how the cut away works and just brain faded. I gave some bad info at another topic regarding the order of the jet needle plastic spacers once too. I gave the reverse order of installation. How? I don't know. I'd only done the job a hundred times and correctly described it before that mistake. I don't think it's really changed anything you've done during this topic, but I just wanted to clear this up.
I'm sure this helps any confidence you have in my posts. Anyway, I take too much pride in my posts to leave bad info out there, so I'm going back to edit out the comments about the larger cut away being richer.

[KEITH KRAUSE]

Rock, I went back and tried to make some sense of the past jetting set ups and their results. The thread is kinda long and it's a little hard to piece everything together, but I'll try to make a suggestion (if you can believe me now.)
But first, your questions about plug colors and throttle position/which jet circuit.
I think the "ash" color is a bit lean. Some will say it's acceptable, but I think if anything, you should err on the side of being rich if you can't get a perfect plug read. I think at least a light tan is what you should insist on.
As for the 1/3 throttle position test and the needle circuit. If you look at jetting charts, they all seem to vary a little. Some show more overlap as the needle rises, some say the overlap is not as much. Flow is so dependent on the specific mods. So many variables. Some charts say the needle has little effect just off idle, but my personal testing says this isn't so. You can go on and on and never get a definite answer. I choose to go with what Mikuni and Suzuki say, more than other sites/charts opinions.
I personally choose the 1/3 throttle position as the best way to test for the needle. At this position, I feel there's THE LEAST overlap effect from the pilot circuit/cut away and there should be no effect from the main. It's the most honest reading you can get, to me. Where I live, I can test at these speeds too and without any trouble. I have even more fun when testing wide open for the main.
As for my suggestion about your jetting, I've said all along the pilot jet should be 17.5 and I'll stick my neck out again. I don't want you to waste any money on jets or your time either. I'd try the 17.5 pilot jets and then adjust the air screws for highest rpm. If you have to "cheat" a little on the screw settings, do so, as long as it's not too much. The air screws are meant to be moved, such as when riding in higher elevations. I still think they'll adjust out closer to "normal" with the 17.5 jets.
As for the needle position, it really depends on how accurate your 1/3 throttle test was. Did you mark the throttle and grip as I do? Did you chop off correctly? Is EVERYTHING else correct? The spark quality, spark timing, valve clearances, synch, float levels... etc?
I would say leave the needles at 3 and re-test with the 17.5 pilots and air screw adjustments. I think the richer 3 needle position will work well. I would rather try 3 first than 2 1/2 with a jetting spacer.
The air screws should adjust out a little more and this will atomize the fuel going through the needle jet better.
This set up should eliminate any heavy exhaust issues you had earlier and give you acceptable plug colors. A little decel' popping is normal, and a small price to pay for the performance increase your mod's have on your motor. There usually is "driveability" issues when increasing power. Sometimes you can't get perfection and must accept the lesser of two evils, if indeed you must choose. A lot of popping, especially during normal shifting, isn't acceptable. But some popping during decel' at mid/higher rev's is acceptable, to me. Especially if richening the jetting just creates worse problems.
Be sure to do a good vacuum synch and triple check the levels after gently exercising the throttle. If you think there's any chance of a sticky slide, you can buff up the carb bodies with some Mothers or Semi- chrome or Blue Magic paste. I would just go ahead and do it if you change the needle positions. Just use a little and run your finger up and down about 50 times per carb and buff out any residue.
I assume any float bowl vent tubes are removed?

[Rock]

I did pick up some 17.5 pilots to try. Unfortunatley it will be a few days before I can try them, I need to get a Pingel valve. I did replace the o-rings yesterday also and went through the carbs and checked the air screws and everthing to be sure they were clean. The slides move easy too without bind. I must say the 0-rings were flattened right out and appeared to be quite old. And I do me flattened. As I stated though I did check for leaks and had no typical signs of leakage. Maybe it's possible this is the problem though? And yes the vent lines are removed.

If this doesn't work out with the pilots I guess my only option will be to try the 1.5 cutouts. Maybe I can find a used set in good condition. The only reason I have not yet gone with that suggestion is the cost. A set or two of pilots is cheaper to try first. I agree this should be easier to tune and that may be the key. I know the other guy here had 2.0 cutouts and said his ran good, but his was rich also. I put a post up to get other members settings on their vm29/s. As always Kieth I appreciate you sharing your experiance and taking the time to help me work this out.