Honda XL 600 LM 1986 not pulling in high revs?

i have posted a question about this before as my new bike ^ rund and starts no problem and pulls well but when over a certain rev it flattens out and wont pull unless i use the throttle very gently, when i open it out fully it will die, i originally thought this was a carburetion problem and i lifted the needle on the high rev carb ,(duel carbs one cylinder), thid didnt fix the problem although it did pick up a little faster, but obviously not the main problem, so i took it all apart again and put the needle back where it was, i also cleaned out the jets in the carb but they looked spotless anyway. so now my question is, do i have an electrical problem here? the HT lead does look like the original, would that give me these symptoms? the spark plug looks like new also and the right colour. is the ht lead connected to the coil? would i need to get it as one unit and could it be the coil also that is putting gremlins in my powerband? any help would be much appreciated. thanks scott ( and thanks spell checker for pointing out i have done 6 spelling mistakes, no wait colour IS spelt colour!!!!) bloody yanks........ :)