TOPIC:

I initially read about the fuel cut off solenoid causing issues and about electric fuel pumps being a good thing.
Since then I have pissed off the fuel pump and refitted the shut off valve.

Your problem may be due to the vacuum petcock. The KZ1000 police models came from the factory with a vacuum petcock. They were notorious for filling the crankcase with petrol. A leak in the diaphragm allows petrol into the intake manifold through the vacuum line that activates the petcock valve. Kawasaki supplies a petcock rebuild kit for them with a new diaphragm just for this problem.

My advice is to use a manual petcock and condition yourself to turn it off. There is nothing wrong with the original petcocks. The main problem with them is that rust from the fuel tank would get into them and make them very hard to turn. They are easily taken apart and cleaned.

Thanks globemaster, but the fuel tap is brand new, so theoretically there should be nothing wrong with it.
But I find it interesting what you said about the fuel finding its way down the vacuum line.
Another avenue to investigate.

Lol never be sorry for asking the question, it was designed and fitted for a reason. The question really is if it was failing why was it failing, does anyone know or have the answer apart from fitting a vacuum operated tap. It is peace of mind knowing your fuel is shut off when ever you stop. I like others have dumped a tank of fuel into my sump then had to go through the pain and cost of replacing oil and a new tank off fuel due to forgetting to shut the petcock off. I refitted one recently and it worked a treat as a positive shut off my garage no longer stank off fuel pissing the neighbors off in the process, however did cause me a problem at full power and did exactly as you said but this turned out to be that the fuel pipe was kinked and restricted the flow. Quick fix for me was revert back and remove initially, I will be trying again with correctly routed fuel pipe. I was never left stranded just had to wait about a minute to allow fuel to top the carbs back up and then limp back home slowly, thank god for UK traffic lights being every 100 yards.

The fuel cut off solenoid is solely a safety feature. It is designed to turn off fuel flow in the case of an accident to help prevent a fire. It was never intended as a secondary fuel cut off to the manual petcock.

With a manual petcock, fuel leaking into the cylinders and on into the crankcase has to come through the carburetors. Either one or more float valves are leaking, or one or more of the O-rings that seal the float valve bodies are leaking.

With a vacuum petcock, fuel leaking into the cylinders can come through a leaking petcock diaphragm or through the carburetors.

It is possible that fuel can boil in a hot float bowl after turning the engine off. The fuel could then enter the cylinders. However, if the petcock is shut off and allows no fuel flow, only the fuel left in the float bowls would be available.

Incidentally, in 1979, I bought a new KZ1300. It was my sole transportation for 5 years. Minimum use was a 25 mile round trip commute. A couple of 1000 mile trips were made. There was never an issue of fuel leaking into the cylinders. I did turn off the petcock whenever the motorcycle was parked.

Speaking of the fuel solenoid, it has a complicated relationship with the safety switch in the clutch lever as well. Normally, the solenoid only opens when the kill switch (right handlebar) is in the "run" position, which makes sense. However, if the bike is off, it will only open when the kill switch is on run AND the clutch lever is pulled! With the idea that it will click over to "always open" when the bike is running (even when the clutch is disengaged).

I swear, the safety systems on this bike boggle the mind....

But, history lesson aside, I agree with ditching the vacuum petcock. Get a manual one, eliminate a variable. Turning it off is good practice anyway. Second step is to check the float valve in carb 3 (cylinders 5 and 6). Does this normally flood with your bike on the side stand? If so, it's probably in the carbs as well- were it just the petcock, I'd expect to see cylinder 1 and 2 flooding first.

Anyway, you have a list of things to ponder. Good luck.