i have an mc21 with an odd problem it has just been rebuilt new main bearings gaskets etc it has even had new carb gaskets fitted the bike runs great but only over 2500 rpm below that it wont run on rear cylinder the mechanic that doing the work for me put a strobe light on it and below 2500rpm the timing is moving so we have an eletrical problem pickup coils pgm3 possibly can anyone help me out here has anyone had a problem like this