Fuel Overflow On My stock 77 KZ650 B1

My overflow tubes from the float bowls are continuing to spit/spew fuel. I have the petcock turned off. I recently replaced the rubber O-Ring in the petcock due to the original 34 year old one got ground up when I turned the tap to reserve one day earlier this year. I still find the petcock hard to turn to any postion. Did I not install properly and fuel is leaking past? I used to think I had a float stuck on one carbs. I replaced the fuel with fresh and have run Seafoam through the tank. The bike runs great. Carbs were recently synched by a tuner friend in his shop. I have turned the fuel off and then proceeded to run the engin until the engine stopped running as in out of fuel. I assumed the bowls were empty. I emptied the over flow tubes but a day or two later when I pinch or move the overflow tubes, I get fuel dumping out as if the floats have over flowed again. This is happening to all of the carbs not just one. Did I not install the O-Ring properly and have a leak at the petcock? Are there other areas in or around the petcock that would cause the fuel not to shut off? I am a bit puzzled here. I really did not want to drain the fuel tank again or puil the carbs. I will if I must. A little help please

Don't pull the carbs just yet, first check the Petcock. Remove the fuel line and check it to see if it shuts off. Then also Check the fuel level in each carb, using a clear piece of tubing from the drains up along the side of the carb body. I t should be just under the Gasket surface of the bowl, within 3mm. Not above it, then its to high.
Check to make sure the petcock will shut off first, from your description.

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Thanks Motorhead and Martin.

Motorhead: I will disconnect my fuel line leading to the carbs prior to my filter and check to see if the petcock is leaking. I will then try your check with clear tubes as described. Very good tip and did not think of this. Petcock first!

Martin: The Petcock is a manual. The early KZs had these vs your, I assume CSR with a vaccum set up. I do agree that something must be interfering with a smooth turn of the petcock lever. It could be a form of corrosion or a build up. I am wondering if I overtightend the screw/s that hold the petcock lever, cover and O-Ring in place. I also was wondering if a shot of Slick 50 spray lube(PTFE-Teflon) would help. I am thinking of disassembling the petcock and trying to get right.

Here is a basic question on maunual petcocks to these (4) Mikuni VM24 SS carbs: If the fuel is allowed to flow freely to these carbs will fuel shut off at some point or simply continue to build and then flow out of the float bowl overflow tubes? I have been told by one or two experienced moto biz guys that the carbs should not allow the fuel to continue to flow out of the overflow tubes. I do not know the details at this time. I may research further and get back here. It has caused some confusion on my part. I can't wait to clear up any confusion and just get the bike to stop pissing on my garage floor!

The fuel level in the carbs is controlled by the float valve, this is a needle and seat. The level is adjustable, and is 100% important to proper function and metering or the air/ fuel mixture. The float valve if working properly, and the fuel level being set correctly, the carbs should Not overflow with the bike level.

Motor, that confirms what I was told as well. I do keep my KZ up on its centerstand so it is pretty level. I will still start with the petcock. But am wondering if I rebuilt my carbs correctly back in 2009. :pinch:

ONE MORE BIT OF INFO, that I forgot til now. The fuel really started leaking right after I got my carbs synched. AND, right after this I took the bike for a weekend trip. On the return leg I went to switch from on to reserve. The petcock did not want to turn. I forced it over and up to reserve while riding. After this, I noticed fuel odor in the garage and then finally saw the fuel on the floor and the overflow tubes leaking fuel. Any feedback on this?

Debris could have been in the Petcock, from the fuel tank. Making the Petcock lever bind. this could be your overflow/ High fuel level in the Carbs also. Debris/ Rust Whatever. You may want to get a clear container, then drain the float bowls and see what comes out, also take the fuel line loose from the Petcock to Carbs and drain it. This will let you see if things are clean. Do you have a filter, between the Petcock and Carbs Tee Fitting? If not this would be a good Idea, just make sure it is for a gravity system, and not for the standard 5psi Car system.

Yeah, could be some debris. I will remove the petcock and blow it out with compressed air as well as inspect everything for fit. I do have a gravity fed filter in place between the petcock and T. Great feedback. AND,thanks for letting me bounce a few things off you guys. Now to figure out how to get out to the garage on my anniversary weekend! :lol:

If the manual petcock is missing the screen filters that fit up inside the tank, or if the filters are torn or damaged, rust/grit from the gasoline is allowed to enter the petcock.

If the petcock sediment bowl screen is damaged or missing, rust/grit from the gasoline can make its way to between the sliding mating surfaces inside the petcock.

The mating surfaces may become scratched and become difficult to turn and won't smoothly interface with each other when turning the petcock, and allow fuel to pass through the petcock even when in the OFF position (and also leak around the petcock lever).

The petcock's internal interface is cone shaped with the female part of the petcock case being metal (supposedly a smooth metal surface), and with the male part on the lever being a hard plastic-like substance.

I have tried without success to restore the scratched parts together by using valve grinding compound, and rubbing compound, and also with wet-dry sand paper, and then resorted to various other desperate measures, all of which were futile. Until a brand new petcock finally saved the day.

Good Fortune!

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Patton wrote: If the manual petcock is missing the screen filters that fit up inside the tank, or if the filters are torn or damaged, rust/grit from the gasoline is allowed to enter the petcock.

If the petcock sediment bowl screen is damaged or missing, rust/grit from the gasoline can to make its way between the sliding mating surfaces inside the petcock.

The mating surfaces may become scratched and become difficult to turn and won't smoothly interface with each other when turning the petcock, and allow fuel to pass through the petcock even when in the OFF position (and also leak around the petcock lever).

The petcock's internal interface is cone shaped with the female part of the petcock case being metal (supposedly a smooth metal surface), and with the male part on the lever being a hard plastic-like substance.

I have tried without success to restore the scratched parts together by using valve grinding compound, and rubbing compound, and also with wet-dry sand paper, and then resorted to various other desperate measures, all of which were futile. Until a brand new petcock finally saved the day.

Good Fortune!

Patton, You win the diagnosis prize! Thank you for your feedback here. I have finally exhausted my options: Rebuilt the carbs, and reassembled the stock 1977 B1 petcock. I am now convinced that Patton's expereience and summary is what has happened to me as well. The inner hard plastic drum of the petcok is somehow compromised. I do not see any surface imperfections. All I know is that the petcock leaks even in the OFF position.

What I need now is a new "NOS" petcock or a replacement for the stock 1977 B1 650 fuel tank. I hope someone knows of a source or has one. Please help! This KZ is really running great since the carb rebuild and synch. I just need to get the fuel to stop leaking. Please note that this is a 1977 with a ON/OFF/RESERVE lever position gravity fed petcock. The distance between the two screw/bolt holes is 1 3/4" Center to Center with the oval rubber O-Ring on the outside of these. I have all the dimensions if anyone is interested. It is a non vacuum diaphragm type but would consider a vacuum type or a pingle type if it would just bolt on or with a simple adaptor plate.

Help!!!!

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