after speaking to a machince last night he thinks its the coil pack giving a weak spark or overheating under load... What do you guys think?
is no 4 plug oily or petrol? if it don't eventually evaporate(petrol) its poss oil, then far more serious,sorry!
Are the coils individual ? Can they be swapped to see if it will blacken the plug on another cylinder ?
Sounds like a fueling prob to me. Has it got vacuum carbs, if it has check the diaphrams for splints and cap seals are all ok and no air leaks etc and if poss when you refit caps push the slides up through the inlets so they seat correctly. If all diaphrams are good do as already said and give all float bowls and jets a good clean out.
stop fkin about & put it on the dyno lol easiest way to diagnose a difficult problem. it will show if its an ignition fault or fuelling issue and a good operator will go straight to it and fix it in no time.
Mate of mine had the same problem with a 600 bandit, turned out to be the jets in the carb. i know nothing about bikes so im just saying
