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First of all, I'm not sure what the problem is so sorry if this happens to end up in the wrong forum......

So, rode the bike to the garage on Thursday, went fine, sailed through its mot, when I went to leave it wouldn't run. Now this isn't the first time this has happened, allow me to explain....

Its a 1988 Kawasaki ZX400G Jap Import
Its just finished a 3 month strip down and rebuild
Bike runs fine until the temp gauge gets to half way (it never goes further than that, never over heats)
Then it will cut out, and the only way you can start it is on full throttle (but the revs never go above 1200) You also need to keep it on full throttle to stop it cutting out (release the throttle, bike dies)

Now, I have two thought. Either its something to do with the bike getting up to temperature - maybe something expands and blocks fuel or air.
Or, it could just be a coincidence that it runs for teh length of time it takes to get warm and be unrelated to the temperature of the bike. For instance, if fuel runs out in the float bowls after 10 minutes of riding, the bike will be up to temp but the carbs have run dry

After its been left for a few hours (usually overnight) it starts up with no problems

Now, I'm fairly new to biking but pretty handy with a spanner so anything you could offer as advice or suggestions to check I would be very grateful

Thanks

when you say it suts out, does it do this whilst riding, or does it only do it coming to a stop?

its probably not float bowls, if it was, it wouldnt want to fire up the following morning - the fuel pump doesnt run if the bike is not running, and because it 'can' fire up when hot its not an electrical problem.

if it cuts out when hot and coming to a stop i would guess its mixture related, all i can think is that you are dumping too much fuel into a hot cylinder, try leaning your pilot air screws.

when did you last strip and clean your carbs including the pilot jets, and when was the last time you had them balanced?

It usually cuts out when coming to a stop. I reset the pilots last week to 2 and a quarter back, but it was doing this before I changed them too

I have something new to add....just been out, same thing happened, cut out after getting home from a 5/6 mile blast. What I did notice is as the fan was going (still after it cut out) all of the coolant in the bike got dumped in to the expansion tank - almost to the point of overflowing. A few minutes later it started to drain back in to the system and is now sat about 1cm below the minimum line, even though I put in exactly the right amount according to the handbook. Does that help?

the fan will keep running to cooldown the colant, thats normal.

its also normal for coolant to expand out of the system into the expansion bottle, and to then get pulled back into the radiator, thats what the expansion bottle is for.

however, yours does seem to be pushing a lot more than normal, maybe the rad cap could do with being tested/new purchased.

still though, if its cutting out, i would hazard a guess that its fuelling related.

set the bike to a slightly faster idle, ~200rpm more than usual, back the air screws off by 1/2 a turn and then see if the bike behaves itself more when hot.

Thanks for the advice. After calling the AA out today it turns out my alternator isn't working, so I guess that's the problem

My bike did exactly the same after a rebuild. Make sure your carbs are set properly but what I noticed on mine is that I only had one fuel filter between the tank and the pump. After a long time searching and trying everything I moved the fuel filter to between the pump and the carbs. Before I moved the filter it did exactly the same as yours cause the bike flooded while riding.