TOPIC:

hardrockminer wrote: 1. Yes, but as the fuel level increases in the bowl you will get increasing pressure on the float valve to remain closed. If fuel continues to flow after the valve is closed then you most likely have a bad match between valve and seat. You should check to see if there is any dirt or varnish on the valve seat that might prevent the valve from closing properly.

2. Depends on whether the petcock is open or closed. If open then the pressure is a result of fuel height in the tank. If closed, and it should be closed when the bike is not running then you must have leakage past your petcock. Either replace it or rebuild it.

3. Maybe...refer to item 1 above.

4. Correct.

5. The fuel system is tolerant of some errors so things don't need to be exactly according to spec.

When you set your fuel level did you check to the top of the meniscus or to the bottom? How did you measure the distance?

I've checked from the top of the float bowl (clear tube test 6 mm +/-1). It's 6, give or take 0,5 for me (vernier caliper).
There is no petcock now. Carbs are on the bench and DIY IV is attached as a fuel source. So, 24 hours of consant pressure. They start leaking after 10 or so.

Here is what the DIY IV looks like (before the bench).



I strongly believe that this is a buoyancy issue.
those floats just sink after some time. They are 40 YO after all.

I was always a big fan of metal floats in my younger days. If they leaked you knew right away by hearing gas sloshing around in them. If it is a float that is being saturated with gas just place them in a cup of gasoline and see if they float. If this is an overnight issue leave them in the cup overnight. If they sink over several hours you will know pretty darn quick if it is a float issue. I can't recall seeing a faulty non-metal carb float in a very long time though. Usually they are more apt to disintegrate for various reasons.

Rick H.

vabi wrote: I've checked from the top of the float bowl (clear tube test 6 mm +/-1). It's 6, give or take 0,5 for me (vernier caliper).
There is no petcock now. Carbs are on the bench and DIY IV is attached as a fuel source. So, 24 hours of consant pressure. They start leaking after 10 or so.

I'd call it done if they seal this well. The petcock will turn off fuel when the bike is parked, or at least it should.

The floats on my bikes are all older than 40 years. And they don't sink. Here is a better way to check your float level. It allows you to watch over time to see if there is any leakage from the float valve. It's the only way that I use nowadays.

www.kzrider.com/forum/3-carburetor/61368...n-setting-fuel-level

hardrockminer wrote: The floats on my bikes are all older than 40 years. And they don't sink.

Same here. Why would they sink unless someone has deliberately punched a hole in them? Ed

Not quite sure if you have access to a laboratory supply in Croatia.
Could you fill up the carbs with your iv setup. Then replace the iv bottle with a burette filled with gas.
The burette will be more accurate concerning fluid loss, but that's if you can get a burette for cheap.

shop.brand.de/en/volumetric-instruments/burettes.html

Nessism wrote:

vabi wrote: I've checked from the top of the float bowl (clear tube test 6 mm +/-1). It's 6, give or take 0,5 for me (vernier caliper).
There is no petcock now. Carbs are on the bench and DIY IV is attached as a fuel source. So, 24 hours of consant pressure. They start leaking after 10 or so.

I'd call it done if they seal this well. The petcock will turn off fuel when the bike is parked, or at least it should.

I think You are right. But...
I'll check the floats in a bowl with gassoline to see if they sink. If there is a buoyancy issue wouldn't there be a problem with fuel level even when the engine is on?

Petcock is modified to ON/OFF rather then vacuum operated. It does not leak at all. In addition, I'll install solenoid valve just to be sure if I forget to turn it OFF.

F64 wrote: Not quite sure if you have access to a laboratory supply in Croatia.
Could you fill up the carbs with your iv setup. Then replace the iv bottle with a burette filled with gas.
The burette will be more accurate concerning fluid loss, but that's if you can get a burette for cheap.

shop.brand.de/en/volumetric-instruments/burettes.html

I've marked the beer botle of my DIY IV so I can see the drop. It's hard to miss because it's significant.
I don't need a burette for that. But, if I try realy hard, maybe I could get one in Croatia. Maybe from the black market.
en.wikipedia.org/wiki/Croatia

Nessism wrote:

vabi wrote: I've checked from the top of the float bowl (clear tube test 6 mm +/-1). It's 6, give or take 0,5 for me (vernier caliper).
There is no petcock now. Carbs are on the bench and DIY IV is attached as a fuel source. So, 24 hours of consant pressure. They start leaking after 10 or so.

I'd call it done if they seal this well. The petcock will turn off fuel when the bike is parked, or at least it should.

Thank You Nessism.
You are right.
If the floats are suppose to do what I want (to withold the fuel indefinitely), a petcock would be unnecessary.
Floats are designed to susstain a certain level of fuel in a float bowl while the engine is running.

So, thank You again.

There is my answer. They sink!!! Two part floats and one of them sink after a few hours. Now I know what to do.

Congrats on making this determination Vabi! How did you finally figure this out? What are the floats made of?

Rick H.

Yes, good job. I've never seen a KZ Keihin or Mikuni float sink but these are TK's so...

As an aside, I rehabbed a ZX6 one time where the floats are hollow plastic. One float was filled with gasoline and sinking so it got replaced. Tossed the gas filled float in my tool box where it still sits more than a dozen years later, and it's still full of gas.