Got a problem, bike will start from cold no problem, runs off choke as it warms, revs no problem, then it cuts dead. It will not restart until its cooled down, my first thought was cdi but checked when it cut out and i still have a spark. I have checked the carbs and they seem nice and clean, checked valves for adjustment, coils check out ok.

Just wondering about the spark as to me it looks weak, i generally look for a big fat blue spark but all i am getting is a very thin lined purple one, any gurus out there with an opinion please shout up with any thought on problem.

Oh yeah its a 1985 GPZ600R (sneaked that one in) i know its not a yam but you gotta go where the knowledge is

Might be fuel starvation undo the fuel cap and try again just in case breather is trapped or something, Other suggestion is try on Prime position on fuel tap.

Tried on prime and it made no difference, but i will give fuel cap a go and see what happens, just strange as it pulls like a train then just dies.

This can happen if vacuum builds in tank, yes!, Can also indicate partially blocking fuel filter, demand is outstripping supply, but if you leave a while carb will fill, can also be something breaking down under temperature on your ignition, you said you checked the coils, check them when it fails!

Finally got to the bottom of it, it was the pickup coils dieing once warm, Fitted another set and all is well>

Thanks for the suggestions Dave C

Finally got to the bottom of it, it was the pickup coils dieing once warm, Fitted another set and all is well>

Thanks for the suggestions Dave C

See...I was wrong again!!

Thanks for letting us know Dave.