hard to start when warm?

[WULFSTAN]

alright lads right the cbr is really starting to piss me off i fix one thing an something else stops. Anyway now she's getting really hard to start when warm and back fired when i did get her going sometimes she dying at the lights aswell. anyone any ideas. i thought it was the spark plugs at first but ive changed them an still the problems continue. bike is 1990 cbr 600 thanks
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Your backside is better enough for you to run again, if need be – bristle up the courage of the cornered rat, put on a bold front, and to hell with them. Bluff my boy – bluff, shift and lie for the sake of your neck and the honour of Old England

[Fizzer Thou]

If you perform a compression test when the engine is warm it might show up as low.Introduce some oil in through the plug hole then reperform the compression test.If the figure jumps up the piston rings are worn.If it stays low the valve seats might be leaking or the valve clearances need adjusting.

It does sound as though the shims need adjusting though,especially if your problem has been gradual rather than a sudden change.
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Just talk bikes.What else is there?

Always have a 'Plan B'

[WULFSTAN]

looks like the feeler gauge is coming out tomoz cheers
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Your backside is better enough for you to run again, if need be – bristle up the courage of the cornered rat, put on a bold front, and to hell with them. Bluff my boy – bluff, shift and lie for the sake of your neck and the honour of Old England