Misfire

[Stratman]

As some of you know, I suffered a front CCT failure. It bent two exhaust valves. When I got the bike back it was running rough so I took it back to the workshop. Further stripdown (all at workshop's expense) revelaed two very slightly out of tolerance inlet valves.
Inlet valves replaced - improvement but a misfire/spluttering at 8000 rpm. Strip down, check everything OK. New inlet tube as one thought to be perished a bit - no change. Plugs OK, balance etc OK. It has completely foxed the mechanic who has 11 years experience and has been working round the clock at his own expense to find the problem, as for him its a matter of pride and reputation.

We also reduced the gearing and he says it pulls like a train in the midrange, but whack it open and you get the misfire/bogs down

Anyone got any ideas, or had this problem themselves?

Thanks guys

[cupasoop]

Check you have got the pipes on the fuel tap on the right way. If you swap them over the diaphram closes, instead of opening, and the thing runs like a pig. Runs fine at low revs but gets worse the higher you go.

[Johnny Wishbone]

Float heights?? Even if one of em was off it'd cause problems. Have you stripped the carbs??

[Pete.L]

You could try covering about half to a third of the air filter with gaffa tape.
If you make the problem worse you've too much fuel going in, (Check your carbs)If you make it better you're running lean.(Fuel starvation check you vacuum hoses,pet rock diaphragm, carbs for dirt ect)
If all that checks out it could be electrical, can you borrow/ steal an ignition pack from someone ?

Pete.l

[Stratman]

Cheers so far guys - I'm feeding all this back to the mechanic who has tried virually everyrhing, but a couple have said about the fuel tap diaphragm and I seem to recall earlier threads about this so I'll search back through the board and look. I'll let you know what the outcome is but its bound to be somenthing really stupid!