Hello, I'm new here and this is my first post and any help will be greatly appreciated. I'm a fully certified automotive technician and work for General Motors on their proving grounds in Milford, MI. I have a 1998 banshee that has baffled myself and every automotive and motorcycle/atv guru I've talked and showed it to. I've run through all the standard fixes and checks and am losing my hair over this (what little is left anyway). Starting a year ago, the right cylinder started to not fire correctly. Yet the left cylinder runs perfectly and has enough power to pull a wheelie without trying. I'm also running a single carb intake manifold that i made with a 34 mm pj carb. Both cylinders are getting good, fat, blue sparks (advanced 2 degrees), both cylinders have exactly 125 psi compression, are definitely getting fuel (plug is wet and unburnt fuel is dripping from the silencer). The motor was due for a freshening up anyway so i put new rings in, new gaskets, new crank seals, new reeds, and lightly surfaced the head. After i was done, i both pressure and vacuum tested the crankcase and cylinders; they held pressure and vacuum for well over an hour. The rebuild made absolutely no difference in the running condition. Knowing the problem must be electrical now, i tried new coil, nothing, new stator and ignition module and checked clearance to the hall effect sensor, nothing, pulled wiring harness apart to check for bad connections or wires, nothing. The only thing i haven't replaced is the CDI box for lack of funds and from everything i've read about the banshee cdi boxes is that when they go bad, it just wont run, not run halfway. Using an infrared temperature gauge, the highest i've been able to get the right cylinder up to is about 140 degrees on exhaust pipe just ahead of the cylinder, where the left cylinder will be well over 300 so i know its definitely not firing right. Observing the exhaust smoke, the left cylinder will shoot out puffs with pressure that is able to be felt from 3 feet away, however on the right, the smoke just "pours" out in a stream out with no pressure at all. My best guess is that the right cylinder is somehow firing way too late in the stroke somehow. Could it possibly be a messed up CDI box? If anyone here has any ideas or experience with a bizzare problem like this, i would be greatly appreciative. Thanks in advance, Matt.
