Removing Main gears from main shaft - 1941 BSA M20
Hi, rebuilding M20 gearbox and mainshaft is no good as K139 keyway has chomped into mainshaft.
New Old Stock mainshaft is available.
My question is - How do you remove maingears (# 24-4231) from mainshaft, are they pressed on?
Thankyou.
Chris
Re: Removing Main gears from main shaft - 1941 BSA M20
Yes it is pressed on. Sometimes they come off quite easily under a press, but on a couple of occasions I've had to use most of the power of my 10 ton press to get them to move, then they go with a bang. I've never been sure if heat would help? So removed them cold. Comments from others would be appreciated. Ron
Re: Removing Main gears from main shaft - 1941 BSA M20
The gears are a press fit on both shafts...Remove using a hydraulic press or large fly press....DO NOT heat the gear or shaft....Occassionally the fit between the gear and shaft has been lost and the gears come off by hand...Replacement parts are the best soluion to that problem...When fitting press the gear all the way home, it will go to the limit without affecting the 'trapped gears' ability to turn but if using a hydraulic press take care not to keep on applying pressure when the gear is fully home...
If you don't have a NOS mainshaft yet I have one for sale at the moment for less than you will usually find one...Contact me off forum if interested....Ian
Re: Removing Main gears from main shaft - 1941 BSA M20
Had to rebuild my box after Normandy 2 years ago
Both fixed gears I removed by hand
It’s amazing how these boxes can still deliver despite the internals being so worn or beyond it
Definitely got my moneys worth out of that one !
