right try to solve this one chaps, the 250 twinport is running a gerrard copping electronic ignition, dellorto carb and gmc pipes and up till three meetings ago ran perfect then at the next meeting it would start to cut out when flat out in 3rd and then 4th gear just at the top of the rev range as though the kill button was being pressed or fuel starvation. stripped carb checked float height etc all fine, plug was a bit lean as very hot day so upped the jetting still no joy, maybe crankshaft seal leaking so replaced that and checked and replaced base gasket and any other obvious air leaks seems to rev out perfect on the stand and when flat out in 1st then into 2nd gear but as soon as you click into 3rd and approach the top of the rev range it just goes buurrrrrrrr so grab 4th and same again pulls hard till top of rev range and buurrrrrrrr.
so any ideas PLEASE? thinking maybe the coil is breaking down at prolonged revs but not sure as have no experience of coils doing this (is it posible for the coil to play up in the two higher gears only?) pretty much covered every thing i can think of other than a crankcase air leak that i cant find though would have thought the bike would run on and generally run crap regardless of gear or revs as have had plenty of experience of air leaks over the years.
please some one give me a clue as im totaly stumped and pulling me hair (wots left) out cheers
