VM 26 ss overflowing

Ok. I managed to get the original manual for my Kz1000 ´77 and identify my carbs. They are VM 26 ss.
Problem is much petrol comes out of everyone of the overflow tubes ONLY when I open full gas and ONLY when the bike goes. It does NOT happen if the bike stands: I can open full gas with no problem or stop engine and leave tap on and is ok as well so I figure out the float valves are ok. I have measured fuel level and it is within the service limits (wet test, with a piece of clear tube, on the bike:2-4mm)
What can make a differece to the carbs if the bike goes or not? Some kind of turbulence blowing the petrol out of the carbs? I am lost.

Do your carbs have an accelerator pump on them?

antokan12 wrote:

Ok. I managed to get the original manual for my Kz1000 ´77 and identify my carbs. They are VM 26 ss.
Problem is much petrol comes out of everyone of the overflow tubes ONLY when I open full gas and ONLY when the bike goes. It does NOT happen if the bike stands: I can open full gas with no problem or stop engine and leave tap on and is ok as well so I figure out the float valves are ok. I have measured fuel level and it is within the service limits (wet test, with a piece of clear tube, on the bike:2-4mm)
What can make a differece to the carbs if the bike goes or not? Some kind of turbulence blowing the petrol out of the carbs? I am lost.

Yea..that's the odd situation for sure..

I have never in all my years of working on bikes run across that..

Sounds like eithe vibration induced or somehow your floatbowl vents are getting pressurized....

Bike fuel system is stock, except two fuel filters to avoid dirt in the carbs. So NO fuel pump whatsoever.
You will think I must be kidding! It seems to happen only under strong acceleration.
I noticed something was not right when I had a slippery back tyre from time to time. Specially starting from stop at a crosslight. After inspecting the tyre and surroundings I noticed this four little black hoses coming out of the carbs were wet at the endings, so I thought they might be spilling petrol over the tyre. I routed them towards the side of the bike to keep an eye on them and realized what was going on. I just need to know why.
Thanks guys.

is it a vacuum operated petcock?

Hi Eddie. It is a hand operated petcock. (on-off-res)
And no difference between on and reserve position...

The accelerator pump is a special pump on the bottom of one of the float bowls that shoots additional fuel into the intakes when the throttle is opened rapidly. If you have one, could it be possible that the check valve has failed and the pump is pushing the fuel back into the bowls, causing them to overflow?

antokan12 wrote:

Bike fuel system is stock, except two fuel filters to avoid dirt in the carbs. So NO fuel pump whatsoever.
You will think I must be kidding! It seems to happen only under strong acceleration.
I noticed something was not right when I had a slippery back tyre from time to time. Specially starting from stop at a crosslight. After inspecting the tyre and surroundings I noticed this four little black hoses coming out of the carbs were wet at the endings, so I thought they might be spilling petrol over the tyre. I routed them towards the side of the bike to keep an eye on them and realized what was going on. I just need to know why.
Thanks guys.

Hi jetskier. There is no pump in my carbs. They are quite simple acording to the manual as well. I know it happened when I had the original air filter system as well so I cannot directly relate the problem with the pods. Maybe an exorcism would help.

Your problem could be alot of things. It is odd that it doenst leak at all times.
It is probably time to pull the carbs off and do some investigating. A few things to check would be;
1)Float valve assemblys - are they tight in the carbs?
I have seen this happen and if the float needle valve assemblies (the screw in seats) are loose in the carbs would leak when they wanted to and stop when they wanted to also.
2)Correct parts? The float needle valve should be a close fit in the float valve seat. It should not wobble side to side.
3) grundge in the carbs passages above the float needles-
if the particles are semi boyant, it may only get pushed down (by the fuel) when the fuel flow is higher, causing the leak as you described.
4) Check to see that the brass over flow tubes in the bottom of the carb bowls dont have holes in them.
Remove your float bowls and put your finger over the inner end of the tube and blow in the other end. They should hold light pressure and not have andy hissing sounds or air leaks.

Are your motor mount bolts tight? The added vibration of loose motor mount bolts could cause the problem that you describe.

It is probably time to pull your carbs and do some investigating. Study your manual, then study it some more and when you are done studying it, Yes, study it some more. Carbs arent that hard to work on and alot of people get scared to take the plunge.
and keep us informed of your findings,
Good Luck !!
Fish

Thanks Fish for the post. Your points make sense to me. I will take the carbs off and check everything this weekend if I have the time. I am already saving for a complete kit, just in case... The only thing that does not look right from the outside is that there are no pilot screw limiters. I did not know of it existence till I saw them on the manual.

I have my VM26SS carbs off my KZ apart right now....so I'm kind of familiar with the overflow tubes and where they are positioned. Is the fuel overflow coming out of just one or two tubes or all four of them. Just one or two could make this a semi simple float problem. Fuel coming from all four tubes would have to be something common to all four carbs causing the fuel level to rise in all of them. Lastly, did anything odd or strange happen (got gas at a new place, engine run wierd, backfired, poor performance, used a new fuel additive, etc.) prior to this problem starting?

John Burke
1978 KZ 1000A2
N.E. Oklahoma

Took carbs off for inspection today. At least one of the floats was sticky (plastic side rubbing against the starter system inner lump) Cleaned everything with Kraft spray and blow the holes with an air can for PC's (I do not have a compressor available at work) Everything was tight. I have changed the air tubes between carbs. I will check fuel level now again with the carbs off the bike and give it a try again.