81 KZ750E-2 carbs overflowing. Any suggestions?

Recently had a fuel leak on #2 carb, so I lowered the float level on #2 slightly and the problem was corrected, for a while anyway.

Last time I went to ride the scooter, found that all four carbs were leaking from the overflow tubes a lot, both in the prime position and when running. No leaking when the fuel is shut off by the petcock vacuum.

I have worked on these carbs in the past, and everything has been working perfectly, until this problem.

Any ideas on what is causing this?

Thanks in advance,
DanAir
1981 KZ750E-2

trash in the needle and seats, or they may need to be replaced they dont last forever

If not already done, would install an in-line fuel filter.

Imo, the service floatbowl fuel level should be adjusted per FSM specs. The float buoyancy remains the same regardless of fuel level, and the float tang pressure against the float needle (pressing it into the seat) remains fixed. Am thinking the temporary leak abatement was due to something else besides lowering the float level, such as happenstance clearing of the needle/seat interface.

For example, the same inner-tube floats with equal buoyancy regardless of water depth.

Good Luck!

I did install an in-line fuel filter last time I worked on these carbs. The ideas you guys came up with make a lot of sense. It just seems strange that all four needle/seat interfaces would foul all at once. It is possible, however, with low quality fuel these days.
Will try external fixes first, since those rubber air ducts are such a son-of-btch to get back on.

Thanks for your ideas,
DanAir

You have CV34 Keihin carbs on that thing, right? The seats are not replaceable. Clean them with Brasso and a q-tip and replace the float needles... the float needles are rubber tipped and if your bike ate some ethanol gas, I have been hearing more and more reports of rubber getting eaten. If you have the carburetors off the bike, set the float levels with the service fuel level method. If all four carbs started puking at once, the only thing I can think of is pinched vent lines... On SOME CV34 assemblies, there is a vent tee between 1&2 and 3&4 and if you have hoses on them and the hoses are obstructed, a vacuum sets up in the float bowls and the floats won't know how to act and the bowls will overflow.

DanAir wrote:

... those rubber air ducts are such a son-of-btch to get back on....

Life's too short to be miserable! :laugh:

Soft and Sensuous

Good Luck!

patton are you a mind reader how did you know that i needed a set of those.

After the information provided by WG I removed the #4 float and needle. The rubber tip of needle looked good (no gum, dirt, goo) and it seemed firm and pointed, like it should. The seat looked good and clean too.
Put the carb back together. Removed the fuel tank, elevated it, and ran a long fuel line from the tank to the in-line fuel filter. Turned the petcock to prime....no more overlow from the bowls in prime, run, nor reserve, running or not.

Now, I'm happy that there are no overflowing float bowls, but I still don't know what caused this. It may happen again on the road. Yikes.

WG, there are no external hoses on these carbs (CV34's) except the fuel line and the petcock vacuum line on #2.
Forgot to mention that I drained the fuel from the carbs before removing the #4 float bowl. What the hay is going on here? Any ideas?

Thanks for your input,
DanAir

OOPS, Still leaking. Seems to be comming from inbetween the carbs, not the overflow tubes. RATS!! Must need removal and parts. RATS!!

sounds like you must have had a piece of crap in the float valve and when you drained the carbs it came out with the fuel.

DanAir wrote:

... OOPS, Still leaking. Seems to be comming from inbetween the carbs, not the overflow tubes. RATS!! Must need removal and parts. RATS!!

Possibly worn o-rings on inlet fuel tee and fuel pipes.


#92055

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Thanks Patton,

The reason I thought it was fixed at first, is the fuel was not flowing from the tank due to a droop in the temporary fuel line. Dumbness!

You could be right. I never separated the carbs when they were off before. Is there a place where these o-rings can be purchased, or does one have to "wing it" with whatever fits? Checked a couple of sites including Z1. They didn't list them.

DanAir

DanAir wrote:

... never separated the carbs when they were off before. Is there a place where these o-rings can be purchased, or does one have to "wing it" with whatever fits? Checked a couple of sites including Z1. They didn't list them. DanAir

Unfortunately, kawasaki.com parts diagram doesn't include the o-ring size. Might try to match at local hardware or auto-supply store (try for the fuel-resistant variety, "nitrile" as I recall). If unavailable, could try wrapping exising o-rings with teflon tape before reassembly, which is a method successfully used on fuel pipes having the built-in rubberized raised seals without o-rings. Other members have reported the teflon tape seems to hold up very well against the fuel exposure. There are also o-ring supply sources on the web with boo-koos of different sizes and materials.

Good Luck!