I've recently acquired an MC21 that for the past few years sat in the weather without much of its fairing. most of the electrics did not work and to date I have repaired the lot apart from the uppermost plug has no spark.
I have tested the pulse generators and even swapped them around and both will work on the front (lower) plug but not the upper one. I've also swapped coils and plugs (new) to no avail.
I have checked all the wiring and connectors through to the computer and from the computer through to the coils etc, and I have continuity and there is no voltage drop between the connections.
Someone has suggested I can grind lobes off the flywheel and that will solve the problem but I have doubts it would work, anyway, I can't see bodgying a perfectly good flywheel makes any sense.

I've noticed the lower pulse gen/flywheel lobe clearance is .010" and the upper (non firing) one is .025". I would dearly like to determine if this is the correct specs and if both pulse gens are in fact identical or if the upper one has a longer pole- mine hasn't, it's identical to the lower one.

I haven't tried to start the bike as yet so really I have no idea if the upper pot will fire up once the front one fires. It might be like some of the Mitsubishi Lancers that need the first pot to fire for the computer to energise, but I'm grasping at straws!

I am a retired motor mechanic with extensive experience in late model Mitsubishi vehicles and specialised in electrical problems but this one has me scratching my head. I don't know whether to buy another computer or to just fire the bike up to see what happens.

Any advice greatly appreciated.