A few questions on VM29 carbs

[Rock]

I did have the floats set. But I was always leary about the needle valves. I took them to a local shop and they said they were good. I was concerned about the weight of the float sagging the spring some what when I was setting the height. Well I put the new needle valves in this morning and it resulted in some of the floats being nearly a 1/16 too high when the new valves were installed. So the floats were actually keeping the fuel low in the bowls. They were wrong. The springs in the new valves were stronger in the new ones.

I have now replaced every o-ring and pretty much rebuilt the carbs totally to rule anything out. I did get 117 pilots but have not tried them yet. Could the low float setting cause a lean burn on the needle circuit?

 

[KEITH KRAUSE]

If you had weak float needle valve springs, that would allow a higher and richer fuel level, not a leaner level.
I can't say this problem would effect any circuit more than the others. It should effect all three the same. Fuel would be too easy to draw. Weak springs, leading to a high fuel level, usually result in some minor fuel spillage out the overflow lines or the filters and a raw fuel smell while sitting.
It would effect the pilot circuit and cause you to think the pilot jets are too large. It could explain why the air screws don't respond as normally as I think they should.
If the floats are reset now, I'd go test first. If your floats have a "range" of setting, I'd put them right at the mid-point. I always set all basic maintenance things correctly before playing with the jetting.

 

[Rock]

I always set all basic maintenance things correctly before playing with the jetting.

I agree with that. I didn't think it was right the springs had some sag in them from the wieght of the bowls when the carbs were inverted to set the hieghts even the the shop told me it was "alright". At this point all o-rings and gaskets have been replaced in the carbs except I haven't taken the jet blocks out and replaced the gasket there. Valves and timing and plug wires have been taken care of also. Thanks for the continued assistance and I'll let you know how it goes. Jim

 

[robinjo]

What is the correct float height for VM29's?

And do or don't they have a connection for the pet cock's vacuum hose?

I know have a pair of these babies!

 

[KEITH KRAUSE]

What is the correct float height for VM29's?

And do or don't they have a connection for the pet cock's vacuum hose?

I know have a pair of these babies!

23 mm on the floats...no vacuum port. Good reason to buy a Pingel valve.
Whaddaya mean "I know have a pair of these babies"?

 

[robinjo]

What is the correct float height for VM29's?

And do or don't they have a connection for the pet cock's vacuum hose?

I know have a pair of these babies!

23 mm on the floats...no vacuum port. Good reason to buy a Pingel valve.
Whaddaya mean "I know have a pair of these babies"?

Ahum... I meant, I now have a set of these babies. :roll: Excuse me it was late. :lol: Thank you.

 

[KEITH KRAUSE]

That's what I thought you meant, but I figured if you had a set, you'd know there's no vacuum port. Anyway, glad to help.

 

[Hoomgar]

mmmm, VM29 smoothies :mrgreen:



Keith, the VM33 smoothies also have no vacuum port? I need to go pingle on my project bike? 8O

 

[robinjo]

That's what I thought you meant, but I figured if you had a set, you'd know there's no vacuum port. Anyway, glad to help.

Just making sure. :wink:

Maybe a weird idea and it could be stupid but what if I took the vacuum from one of the synch holes in the head? Make a 5 mm bolt, drill it in the center and make it extend 10 mm so I could put on a line? The stock vacuum port is also after the throttle slides. Or use the stock petcock on Prime, turned back to On when not ridden.

I have read this entire topic, excellent reading material!
I checked out my carbs yesterday to see what's in them, here is what I found:

Float height 22.3 mm

Needles 5DL31 middle position, no shims on top or bottom

25 idle jet

120 main jet

Throttle slide cut-away 2.0

pilot screw

#1 1 full turn
#2 ? turn
#3 just over ? turn
#4 just over ? turn

Now all ? turn out as starting point

Warmed her up and adjusted for highest idle

#1 ? turn
#2 a little over ? turn
#3 a little over ? turn
#4 a little over ? turn

Did this using a small gas container since my tins are getting paint (when I get to it again) so test rides are not happening right now. These carbs came of a GS1000, I have bought new K&N filters for them and put them on,

do you suggest ordering the 17.5 pilot jets and 115 mains?

 

[KEITH KRAUSE]

mmmm, VM29 smoothies :mrgreen:



Keith, the VM33 smoothies also have no vacuum port? I need to go pingle on my project bike? 8O

No vacuum port on the 33's either. I always recommend the Pingel valve.
I've only had a hand in jetting one GS1000 with the 33's many years ago. That bike as I remember had my mods plus some light porting/polishing and a cam (can't remember what kind). We did get the bike to fly at higher speeds but around town driveability was ill mannered. The bike just wanted to go fast. Throttle response was way too sensitive. I hardly consider myself "good" with these carbs. I've forgotten what little I did learn about them.
You may have better luck with your bike and your specific mod's, plus you say your builder knows these carbs. They're a bit too large in my opinion and hard to tune, but I hope you'll fair better.

 

[KEITH KRAUSE]

Robin, you can get vacuum the way you described.
You could also run the stock petcock on prime as you said, and turn it "on and off".
Personally, I'd buy the Pingel. But to each their own.
It's real late for me, so I gotta go. I'll comment about your jetting later if you still need suggestions.
But yes, I still think the 17.5 pilot jets (at least on Rock's bike) will work. Not sure about the mains. He's had a lot of richer/leaner back and forth problems, especially the pilot circuit. What kind of exhaust you running? Other mods besides the K&N's?
Talk to you later.

 

[robinjo]

Robin, you can get vacuum the way you described.
You could also run the stock petcock on prime as you said, and turn it "on and off".
Personally, I'd buy the Pingel. But to each their own.
It's real late for me, so I gotta go. I'll comment about your jetting later if you still need suggestions.
But yes, I still think the 17.5 pilot jets (at least on Rock's bike) will work. Not sure about the mains. He's had a lot of richer/leaner back and forth problems, especially the pilot circuit. What kind of exhaust you running? Other mods besides the K&N's?
Talk to you later.

Alright Keith, I will get the 17.5 pilot jets, I will probably have the bike dyno'd for the top-end so I will leave the main alone for now.

My bike has stock cams and pistons, head is also stock I believe, bike has points ignition with new points and condensers, very nice spark, the bike either has way taller gearing or a close ratio gearbox, it does 60 mph in first gear 8O and 62 mph@3700 rpm in fifth. The bike is equipped with a period Bos Mach I four into one exhaust which is quiet-ish, not a straight through muffler. Intake boots and O-rings are brand new, valves are set, will synch the carbs when it is road worthy.

I think I will take vacuum of the synch port, this option still lets me use Reserve, petcock flows very nice btw, drains the tank pretty quick, it has been cleaned and inspected.

p.s. what is the stock number of teeth both front and rear?

 

[KEITH KRAUSE]

Remember Robin, I'm still learning about these 29's too. So don't take my word as the way it is.
As I've followed Rock's re-jet attempt, I still think the 17.5 pilots will work. I think the larger pilots are causing the air screws to not operate as they should. Your current air screw settings suggest a similar pilot circuit problem.
As for the needle, I think the 3rd position will work, but this is based on Rocks bike. Until you're ready to test ride, I can't say.
Same for the main. You also said you may just Dyno the bike. I would stay with the 120's anyway and test them first. They MAY be rich, but it's always better to start on the rich side, than lean.
Just make sure those carbs are super clean inside and the floats set correctly before the tests. Synch carefully. Remove the two float bowl vent lines too.
The stock gearing is 15/42. My bike is similar to yours in rpm/mph. 55/60 in 1st, and 67/68 at 4,000 rpm.
Let me know how things go. Rock, if he comes around, may benefit too.

 

[Hoomgar]

Robin, like Keith said, 15/42 is stock teeth. And my gearing is also very close to what you have as far as how fast at what RPM.

 

[robinjo]

Oh allright then, maybe I will add a few teeth on the back when it's road ready, maybe not.

 

[Hoomgar]

Oh allright then, maybe I will add a few teeth on the back when it's road ready, maybe not.

I removed 1. It's now 41. Taller is better if the engine is strong :wink:

 

[Rock]

It's been a while since I posted any progress here. I repacked the muffler as the old glass was not wrapped tight any more and pretty much just laying in the muffler. Not so loud now either. At this point three plugs are looking good on the 1/3 throttle test. The only thing is that #2 cylinder is running lean. I am going to replace all the intake boots before I go any further. They appear to be in good shape, but one of them (not # 2) does have a crack in the rubber at the flange where the screw goes to fasten to the head. This is where it covers the metal flange. It doesn't appear to go any further. There is no cracking or dry rot visible. They are twenty seven years old so I'm just going to replace them. This will pretty much completely have replaced all gaskets, o-rings and boots other than the thin gasket that are under the jet blocks. Looking at the screw for the blocks it doesn't appear they have ever been removed before.

I have had other problems than the bike taking my time, so I have been riding it as is when I get the chance. It is running well and I still am running the same jetting I was before I repacked the exhaust. If I can find out why one is lean I think I'll be all set. I haven't tested the pilot circuit again since I repacked the muffler and I am just going to wait until the boots come in.

 

[KEITH KRAUSE]

Allright. Let us know how things go.

 

[Rock]

My boots are not on the bike yet but I was wondering what else could be responsible for #2 cylinder running leaner while the rest are fine. I really don't think it's the boots, but it may be. I have swapped slides around in the carbs already to see if maybe there was a problem there, nothing. It doesn't idle high either to suggest a vacuum leak. Could it possibly be the valve adjustment? I did go through them before but would check again if that could be it.

Also the #2 cylinder that is some what lean is the same one the carb with the accelerator pump is on. I did replace the diaphram with a new one though when I finished cleaning the carbs. I wonder if the other carbs could be pulling fuel away from #2. Is that a possibility? I'm not sure but I think it only pumps gas to the other carbs on the intial twist of the throttle as it pushes the diaphram so I'm thinking that is not related to the lean condition. Any other ideas?

 

[robinjo]

Weird problem overhere. :?

Bike is running but on 3 cylinders, it is getting good spark everywhere but #2 is getting no fuel while the bowl is full, exchanged float needle+float needle seat and float itself with two other carbs in the rack two times but no change.

This is through the entire rpm range, not just idle, pipe stays cold no matter what, even checked the compression but it's about the same as the others. Idle jet and main jet are clean.