misses when hot and backfires

[jpmilling1981]

hi all

I have a zxr750 j2, After about 30 mins when the engine gets quite hot, the engine develops a miss, one cylinder seems to "drop out" and power drops plus rev counter also drops to zero. It cuts in and out intermittantly and will sometimes back fire. Once the engine cools it starts and runs well.

its had new plugs, carbs stripped, cleaned and balanced. i've tested the coils, leads, caps and pick up coil.

can anyone help?

thanks jp

[ross46]

when you say quite hot, how hot do you mean? is the fan kicking in? if its not then the mixture might be being changed by the heat. before i sorted the fan on mine it would get half way up the temp gauge and run like a sack of s@#t

[jpmilling1981]

hi,

the fan still cuts in ok and the temp gauge never reads above half way (its not long had new thermostat, temp sender and fan switch). when i say hot i just mean after a good blast when up to normal running temps. when it first starts playing up it wont rev above 9k. its like hitting a limiter yet will rev fine when stationary just not under load.