Leaking fuel out overflow when park - 1980 KZ440

Hi everyone! New here, first post. I tried using the search function to find a solution but there is so much to sift through. I will delete this post if it is too repetitive.

I picked up a 1980 KZ440 yesterday - it is my first bike and I am really excited to dive in. I am mechanically inclined and have rebuilt a few carbs before but wanted to check here for any specific advice.

One of the carbs is dumping fuel out of the overflow when the bike is parked.

1. The carbs have no hoses running off the overflows, is this a real problem or are the hoses just for directing overflowed fuel off the engine?
2. The carb that is leaking has a cap on the vacuum connection, the carb that is not leaking has a vacuum line running to the petcock
3. I plan on rebuilding both carbs, are there recommended kits to use?
4. The fuel leaking is cyclical, like a bell siphon or something. I think the bowl fills and then all the fuel dumps out and the filling starts again. Stuck/defective float? Shouldn't the petcock stop letting fuel flow when the bike is off?

Thank you all for the wealth of information and any future help you may provide me directly.

The engine also has a tick but that is the next issue to be addressed Obligatory pic of the bike included.

1. For safety's sake it's important to run small tubes to the side of the rear wheel just in case you have a stuck float and the carbs overflow. Dumping gas on a hot engine is never a good idea.

2. Be sure those lines are vacuum and are not vents.

3. Do not purchase aftermarket carb kits. Keep all the original brass jets and such and only replace what you need, and use OEM Kawasaki jets as need be, not aftermarket.

4. Yes, the petcock should stop fuel flow when the engine is off (no vacuum signal) unless the lever is set to PRIME. Be sure to set the lever to either ON or Res, and then verify fuel flows only when there is vacuum pulling on the diaphragm in the petcock. Also make sure there is no raw gas backflowing down the vacuum line and into the carbs that way as well.

Touching on just one of these answers for now (4): so if I am continuously leaking fuel out of this carb when the bike is off, the petcock has to be defective, correct?

jlouis wrote: Touching on just one of these answers for now (4): so if I am continuously leaking fuel out of this carb when the bike is off, the petcock has to be defective, correct?

Yes, but there is also a problem with your carbs.

The stock petcock is the vacuum type and these often fail when the rubber diaphragm inside them becomes worn or damaged. You will need to rebuild the petcock if you can find the correct kit or replace it. Considering the fact that a bad diaphragm can sometimes permit fuel to flow down through the vacuum hose and into the cylinder you certainly need to correct this problem

The carbs each have a float valve that is engineered to shut off the flow of fuel when the fuel inside the float bowls reaches a given level. If you carb(s) continuously leak the float valves are not working (they may simply need cleaning), the fuel level is set too high, or, if your cabs have them, the overflow tubes inside the carb bowls are cracked.

Ed

Does the petcock have a PRIME position?

Nessism wrote: Does the petcock have a PRIME position?

Yes it does,

jlouis wrote:

Nessism wrote: Does the petcock have a PRIME position?

Yes it does,

If the lever is set to Prime fuel will flow even if the engine is off. That's what the Prime setting is all about.

Nessism wrote: If the lever is set to Prime fuel will flow even if the engine is off. That's what the Prime setting is all about.

I am aware of this actually, thank you for pointing it out though. I think I need to rebuild/replace the petcock to start and then work on the carbs.

Can anyone recommend a good aftermarket petcock? I know it is ideal to keep it OEM and just rebuild, but I would like to have a petcock with an "off" position. In case the vacuum fails on a road trip, I want to be able to shut off the fuel.

Maybe rethink getting a free flowing petcock with only an On, Off, and Res.
If you hop off the bike and forget to turn it to off you will flood the carbs, possibly the engine with fuel. Once it is working properly, the vacuum petcock might be the way to go.

Conspiracy wrote: Maybe rethink getting a free flowing petcock with only an On, Off, and Res.
If you hop off the bike and forget to turn it to off you will flood the carbs, possibly the engine with fuel. Once it is working properly, the vacuum petcock might be the way to go.

Yea, I get this. I was more looking for a vacuum petcock that also has an off position.

I don't believe there are any vacuum operated petcocks that have an "off" position because the idea behind a vacuum operated petcock was to eliminate the need to turn the petcock off. Personally, I prefer the manual petcock (ON; OFF; RES) on my KZ650-C1. I haven't found it hard to remember to turn it off since I do that when I turn the ignition key off. Of course, I've been doing that for 40 years now so I guess one could call it a habit. Ed