I have a problem with the gearbox of my WM20. When downshifting I have no second gear.
The gearbox goes well in 1st gear, the neutral is also easy to find. Shifting from 1st to 2nd and then 3rd and 4th gear is also smooth. Switching back from 3 to 2 is not possible. The gear lever moves but you ''feel'' that no gear is being selected.
If I then switch back to 1st gear, I can go back to 2nd gear just fine.
The gearbox has been overhauled. All bushings and springs have been replaced. The end play of the axles is also good. I have also adjusted the length of the ''shift arm'' behind the cover. This has no effect, except that I end up not being able to select 4th or 1st gear.
If I carefully try to shift from 3rd to 2nd, very carefully raising the lever, without the clutch, it often works.
I don't know what to look for anymore. Anyone have any ideas?
That is why BSA put the inspection cover on the back of the gearbox. You need to remove it and look inside while you put it in to 2nd gear. That will tell you what is not adjusted correctly. Could be shimming or the change mechanism is not adjusted correctly.
This M20 gearbox is not one of BSA's better designs. A bike like a Matchless or Triumph, has no shims and nothing to adjust. They just work!
