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Hi Globemaster, I actually am interested in this subject, nobody to date has give me an answer to this problem apart from they were a problem, so people did away with them. I have 4 of these bikes non are fitted with the solenoid and through me forgetting to shut the fuel tap off have managed to drain the tank to sump on occasions over the years. So refitting the solenoid if all works well sounds like a good secondary safe guard to me. I am going to digest your post on the electrics you explained that simply and well, I think this has been a great debate to re-ignite. I am a great believer in the root causes, all to often on whatever subject I think we can easily miss them, but if we can get to the root it probably clears a lot of other problems and saves a lot of heartache.

Hello Mark, Like you, I believe in identifying the root cause of a problem before a real solution can be implemented. If a reliable fuel valve is used, there is nothing wrong with using it as a redundant fuel cut off. I would love to have examined your KZ1300's that had the fuel tank drain into the sump. Do you know what the exact path of fuel leakage was?

Thanks again all for your input, it is greatly appreciated.
Another update.....
As I said I have swapped out the old needle valve clips and , I know I will get alot of flak over this, but I also swapped back to the original needle valves. I set the float heights ....again, but this time, again expecting flak, to around 9 - 10 mm. Paranoid about flooding now.

Refilled with fresh oil and filter.

Refitted everything and cranked the old girl up.
Again she fired up first time.
Re-adjusted the idle mixture and then set about synching the carbs, which I initially set on the bench.
I couldn't believe it, they were almost perfect, just abit of minor tweaking.

I also meant to mention that at the time of rebuilding the carbs , as I had heard that when you run a 6 into 1, staying with original main jets richens things up. So I changed them to 100s. Maybe should go for 105s.

Anyway I went for a run and things went pretty well. I do believe I have an issue with the new fuel tap as I had to swap from the main position to prime to keep her running, but when I did she ran beautifully. What an awesome bike to ride.
Apart from a small flat spot on initial acceleration and the carbs hanging up a little, ie taking a bit of time to resettle to a nicle low idle things are looking good.

Still feeling a little paranoid about the flooding issue, I have decided in the interim that I will use the vacuum tap as a manual tap. I will select prime while I run it, and switch to main when I am stopped. Will be be getting a manual fuel tap asap.

Great news! Nothing wrong with using the original float needle valves if they are good.

Yes, running the 6 into 1 header will increase exhaust gas velocity, which causes the intake gas velocity to increase. The increased intake velocity will make more fuel flow through the jets, causing a rich mixture.

The new fuel petcock does seem dodgy, especially since you had to switch from main to prime to get her to run. Switching to a manual petcock is definitely the recommended procedure.

The small flat spot on acceleration might be carb jetting or could be an ignition timing problem.

Forgot to address the initial flooding problem. If the vacuum petcock was not in prime position when you parked overnight, there should have been no fuel flow from the tank to the float bowls even if the float valves or the float valve housing O-rings leaked prodigiously. Therefore, if the petcock was not in prime position, either fuel leaked past its cutoff valve or fuel leaked through a rupture in the diaphragm. It's possible dirt or rust could hold the petcock valve open. Then, internal float valve leakage would cause the flooding you encountered. This cannot happen with a manual petcock that is turned off.

Thanks globemaster, I will be getting a manual fuel tap as soon as funds allow. I might try to get some 105 main jets and swap them out. May even try to do it while the carbs are in place, see how I go

There are a few threads on the site regarding the needle seat clips and the needles hanging up due to the shape of the clip and the old clips are much better than the ones provided in the rebuild kits.

You shouldn't play around with the float height. It has an affect on all of the fuel circuits in the carb. Changing from the 6.5-8.5 up to 9 to 10 will cause all of the carb circuits to run on the lean side and as you've mentioned a slight stumble just off idle is evidence of a lean set up.

Your problem is with flooding when it sits at rest. Stay focused on the problem and don't go messing around with "other things" The clip is most likely the culprit here. Also, you need to figure out why the fuel tap has a restricted flow while on the main. There's definitely something going on there.

KB