A few questions on VM29 carbs

[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.

 

[KEITH KRAUSE]

Just another quick thought. Are the air jets removable in the 29's?
If so, does Jeff or anyone know, was there a standard air jet size? This jet feeds the air screw, so it obviously could factor in.

 

[Rock]

Yes, they are removable and are available in different sizes. I had them out and cannot find a number on them anywhere. They are very small. The air jet that was supposed to be standard for the gs1000 set up carb is the .9 jet. I may pull one again and lightly polish the outside with steel wool and look with a magnifying glass again to try and find some identification marks of some kind.

 

[KEITH KRAUSE]

OK. I was just wondering about the air jet size. Not trying to complicate things more.
I really think the set up I suggested will work. The only possible problem could be some popping at decel', but I'll keep my fingers crossed. Be sure to synch well, etc.
Trying to get a smooth transition from the pilot to cut away to needle is what we're after. I sure hope it works.
I'm going on vacation beginning this Saturday morning until the 21st. I know you said it will be a few days to try any more tests. I won't be around a computer (probably a good thing.) I hope when I get back you'll have good news. Good or bad, let us know.
If I can, I'll post again any thoughts or a "plan B" if I have time. Good luck.

 

[Rock]

I was able to see a number on one of the air screws. They are 0.9 You really need a strong magnifier to see the numbers. According to the information on Sudco these are the proper jets. Have a great vacation.

 

[KEITH KRAUSE]

I was able to see a number on one of the air screws. They are 0.9 You really need a strong magnifier to see the numbers. According to the information on Sudco these are the proper jets. Have a great vacation.

Yeah, I'm sure they're fine. Was just wondering about them.
Hope to read good news when I get back.

 

[Rock]

Here's the update. I took Keith's advice and replaced o-rings on intake. I also replaced plug wires, checked timing on Martek unit, o-rings on air screws. I did move the timing mark slightly as it was just off the mark a tiny bit, maybe 1/16 of a inch. I also re-oiled my K&N air filters. I has them oiled very lightly (barely) before and maybe not enough. I also installed a Pingel valve. I would think most of these would cure a lean problem, not a rich one. I also went back to all original jets to start over from the beginning. I now have #25 pilots, 115 mains, and needle on middle clip as it was when I got the bike.

It now runs PERFECT on the pilot circuit, a nice tan color at 35 mph chop test. I also ran a few at 40mph and it does show a little leaner but still a light tan to ash color. So I'm assuming the needle is getting ready to come into play at a bit more throttle and supply more fuel.

It is now lean on the needle at 1/3 throttle. I mean white clean plugs. I figure I need to now raise the needle a notch and try it. Hopefully it doesn't screw with the pilot circuit. I'm going to try this today or over the weekend. I hope my floats are not to low and causing this now. It runs like a bat out of hell at high speed though and really pulls with no hesitation.

Even after just riding around the plugs show no richness at all. I don't know what of the above changes fixed the rich pilot problem but I happy to have finally get some where with it. Every thing has turned around 180 degrees. The mix screws are now set at 1 1/4 to 1 1/2 on all carbs. I had spark with the old wires, do you think the new ones may provide a spark that much hotter to change this? And to look at the spark it is blue but I'm not real impressed with the strength of it. My lawnmower provides more snap than this.

 

[jeff.saunders]

Glad you are making progress. It sounds like you are very close - raising the needle may get you where you need to be..

The spark from stock coils and old wires is not very impressive. If you compare to aftermarket (Dyna, Accel, etc), you'd be amazed at the difference.

The wires do deteriorate with age, as do the coils. Often replacing wires and plug caps helps - but on many of these older bikes, the wires are molded into the coils making replacement tricky or near impossible. You can buy NGK cable splices - but considering the price of them (about $27), it's better to put that money into a new set of coils. $110 gets you a set of Dyna coils - another $16 gets you a set of wires.

A good set of coils will help give a cleaner burn - it allows you to run a touch richer with less fear the plugs will foul.

 

[Rock]

I do have Accel coils that came on the bike. I checked them for resistance and that was fine, about 3 1/2 ohms. They have a blue spark but you can't hear any snap like I have seen on other types of engines. It doesn't seem like a very big spark either but maybe that is normal? I don't know any other way to check them. They are I'm guessing well over ten years old. This bike was parked for ten years and I don't know how much use they saw before that but I can tell they have been around and probably used for several years. I will try and find out.

And anyone needing Mikuni parts, Jeff is the guy . I ordered some on Tuesday and had them in the bike Thursday. My order before this one from him was handled quickly as well. Great service Jeff!

 

[Rock]

Well I raised the needles up one notch and everything went black. Pilot circuit included. Not as responsive either and seemed a bit boggy on take off. One mistake I may have made was I replaced the mix screw o-rings after getting a good read on the plot circuit and did not check the needle circuit again before changing the needle height. The o-rings were about .012 bigger than the old ones and wonder if I was sucking air through the old ones giving me the lean burn. I think I will go back and retry the middle position on the needle before trying a spacer. I did not sync again yet but the all the plugs were so black I didn't want to spend the time to do it unless the plugs looked good.

edited to add,I also changed the plug gap to .035 as suggested for Accel coils rather than the stock specs that call for .030 gap.

 

[KEITH KRAUSE]

Just read the latest. Getting late and I gotta work this morning. So I'll be brief and maybe offer some help later.
I still think the needles in position 3 and 17.5 pilot jets with the air screws adjusted for highest idle followed by a good vacuum synch will fix you up ( even if you think it doesn't make sense) .
You also mentioned a possible float level problem?? I thought you had them set?