Just rebuilt the Mk3 Commando after the inevitable layshaft bearing failure. Read the manuals, watched the Norton Owners Club video of the gearbox strip & rebuild, and did the job. Very straightforward.
It all came apart OK, I relaced the necessary parts and it all went together with no difficulty and no parts left over.
Put it back in the bike and I now only seem to have neutral and first gears, and a box full of neutrals where the three upper gears normally live. It makes 'selection'-type noises, but won't engage a gear. The lever moves OK, and neutral/first are easy to select.
What have I overlooked? I know someone will pick this up really quickly and I hope you are going to say I just have to tweak something, but I suspect I am going to have to strip it again.
#1. "RE: Commando gear selection" In response to Reply # 0
If you take off the outer cover and operate the selector fork can you find all the gears?
If not you probably have got the timing on the cam plate wrong.
If all the gears are there then it is probaley a selection spring or selection ratchet problem. Make sure the half moon shaped selector ratchet is located as per the book and that it is not moving out of position when you put the cover on.
#2. "RE: Commando gear selection" In response to Reply # 0
It could also be your gearshft stop plate is stopping your pawl carrier from moving high enough. The stop plate has a small amount of play on it's mounting bolts and it can make the difference between being able to select gears or not.
#3. "RE: Commando gear selection" In response to Reply # 2
Finally fixed it!
After two stripdowns without fixing the problem I decided to put it together one piece at a time, making all gearchanges, camplate movements, quadrant, selectors, gears, etc, at each stage. When I found the problem I felt really stupid, but I bet I am not the first to do it though maybe one of the few to own up...
I had put mainshaft third gear in the wrong way round. The thing is, it all fits in OK. It's just that the selector eventually reaches a point in the camplate that it won't go past. Stupid me.
So, if you do your gearbox, remember to check this. The worrying thing is that it all goes together OK despite this mistake.