Leaking carbs

I have a set of 29mm smoothbores on a 1075 KZ motor. Motor is stock otherwise except for a header. After cleaning carbs and setting floats at 24mm(tried 23mm but carbs overflowed a lot), the #1 carb keeps overflowing. It has for some time off and on. I would check the float setting and it would stop but lately, it's just becoming a pain in the ass. Any ideas what is causing the overflow? It seems to only be #1 carb. I am thinking the float needle may be bad but would like some input on this. Anybody been through this and had any luck correcting the problem?

sounds like a backyark mechanic fix but did you try tapping on it? maybe there is a little piece of rust or somthing stuck in the seat. if not, needles and seats are not to expensive

Well.....I've had the carbs apart more times then I want to say, and I'm sure they are clean after the cleaning I put them through. They don't leak right away. Turn the gas on and you have to wait for 5-10 minutes before they start leaking or overflowing. Gas is coming out the throat of the carb which to me means float needle isn't shutting off the gas. I've tried moving needles around but no help. Looks like new needles and seats might be in the future but wanted to see what all you pro mechanics out there think.

Racer...are You 100% SURE that there's no fuel leaking out of the UNION between carb 1 and 2?
You mention that "carb #1 keeps overflowing"...but there aren't overflow lines ON the 29mm smoothies.
Where exactly do You see the fuel overflowing FROM?
I remember on My 26's(before I installed 29's),I had fuel seeping around the bowl on carb #1 and I thought it was the bowl gasket...put new ones on...same thing...fuel would seep from the "T-fitting" on the 26's and I swore that it was coming from the bowl gasket...but it wasn't...it ws FORMING around the bowl,making Me THINK that it was the bowl gasket.
I used some teflon tape on the fittings,and it worked til the day I switched over to the 29's(about 3 seasons)
Get in there ans have a real good look,Bud...

(I reread Your last reply,and I see that You DID mention where You see the fuel leaking from,but still...have a good look to be sure that it isn't leaking from the union)

Post edited by: Sandy, at: 2006/05/22 22:16

Racer...just sent You a couple u2u's but if I'm correct,I should post it here too.Where do You have Your vent-line connected on the carbs?

Is the bike being operated when the overflow occurs? Is it parked and then overflows? A little info would help. There is no overflow drain in a VM29. If the bowl overflows, it comes out the needle jet then, of course, will pour out both venturis... not only the obvious intake venturi but the engine side venturi as well. This gas disappears into the combustion chamber so I would change oil. If your problem is occuring when the bike isn't running, then shut the gas off at the petcock every time you park and set the bike on its centerstand. NO needle and seat is perfect... they are designed to work when the bike is running and not be a shut off valve for when it isn't although they will MOSTLY shut gas off. The #1 carb is on the down side and tends to leak the most when the bike isn't running. Next, if the leaking occurs when the bike is running, then that is a problem. FIRST thing to check is that the float seats have the proper little screens attached. This keeps the crud that IS in your gas tank from reaching the seats/needles and getting between them which keeps them from seating. If you haven't ALWAYS owned these carbs, many folks don't adjust float height correctly (bending JUST the tang) and will bend the whole float. This changes the floats reference and using the float height measuring technique is kind of useless. You can TRY and bend them back to their original orientation but it is tough... if this happens, you will need to measure the amount of fuel on the INSIDE of the bowl after filling them and adjust the fuel level on the #1 carb to where it is identical to the other carbs by measuring the level of the fuel so it is the same as the others by removing the bowls... that is, measure #2 for instance from the bowl edge to the gas, then measure #1 and if #1 has more, then bend the tang up to allow less gas and repeat the comparison... last, you may have a bad needle and seat. www.Z1Enterprises.com carries replacement smoothbore needles and seat assemblies. They ain't cheap but may help fix your problem.

Also...and I remember Jeff mentioning this to ME,when I was going through My 29's...the floats will sometimes come into contact with the carb body itself,causing the float to hang up.If I remember correctly,the remedy for this,is to gently bend the floats in the opposite direction of where they come closest to the inside of the floatbowl.I can't recall if there's much side-to-side play on the floats(riding on the pins),but I don't think there is.Have a look and make sure there's clearance on the floats.

And on the vent lines?...when I first got My carbs all cleaned out and floats set,I made the mistake of bridging the vent line from one set of carbs,across to the other set,creating a vent-lock,which resulted in fuel seaping out the air-side of the carbs(same as You desrcibe)...DO NOT DO THAT! LOL...run 2 seperate lines from the vent nipples,and route them so they hang over Your swingarm pivot somewhere.
I'm guessing that COULD be why You're getting fuel seeping out the airside of the carbs...hopefully,cause that's an easy fix.
Other than jetting,I haven't had ANY problems with the 29's since then.(still working on jetting,but I will get it)
:whistle:

Well, first...it is the vent lines that WAS leaking gas...I've always called them overflow although I know they aren't overflows. Guess I better be more accurate. They are running down the back of the motor to the swingarm area like they should be. They haven't been a problem since I have set the float level. The gas is coming out the throat. The contact problem did present itself a time or two, but I caught that and made sure the floats were free. I think that's what happened when the pipes started glowing to start this mess. The bike runs great now, it's just that the #1 carb leaks WHILE IT ISN'T RUNNING. I checked with Jeff and he is out of the needle and seats but have some coming so that is my next option. I have owned these carbs since new, so any work on them has been done by me. I'm thinking needle and seat problem but like WIREDGEORGE says, I may just have to shut off the gas when I park it. This has been a problem off and on for awhile so it may just be the carbs way of making sure I pay attention to them. Like they say...if it has a skirt or a motor...you're going to have problems with it!

Checked the carbs real close and they are not leaking around the 1-2 carb joint or the vent hos. It is coming out of what I'm going to call the air jet on the bottom of the intake side throat. Never seen that before but the gas level must be high either from float level(dont think that's it though) or from just the lean of the bike. Didn't want to leak when I put the bike upright, so... Just out of curiosity, why wouldn't the other carbs leak out of this jet if #1 one does? I know #1 is the lowest, but all the carbs are on the same angle. Any ideas?

OK... got enough info now. Problem is, you MUST shut the gas off when parking the bike. ANY float seat on ANY carburetor will leak if the gas isn't shut off. That is why Kaw went to vacuum actuated petcocks... the owner doesn't need to remember to shut off the gas. Don't bother with float level, float seats/needles or anything else... just start shutting off the gas and it also helps to park on centerstand. Also, change you oil, it is gas-fouled and the gas in the oil dilutes it to the point of possible engine damage.

For the record...I too,usually turn My gas off when the bike is parked,but there have been times when I forgot to...and not one sign of any gas leaking anywhere on the carbs,the next day.(and I have no center-stand)
Once I got the vent-line issue figured out,I had no problems with gas leaking at all.
I had the tank and carbs off all winter,but all of last season(which was a shorter season than normal,due to the engine rebuild) there were no leaks at all,and none so far this season.(knocking on wood)

Looks like what I'll have to start doing. Never had this problem to speak of before, so thought I was missing something. I don't run a center stand, so off it goes. Think I'll get me a Pingel petcock...mine is a little stiff and a pain to shut on and off. Yep, tried oiling it and getting it loose, but no luck.