I have a qestion abouth the BSA M20 gearbox i have make a complete overhoul and found nothing incorect but the problem was and is the gear change from the second to the third gear is not going as smooth as it should be. anny help and advice please. Gr. Theo Schipper
Hi Theo
It might be something as simple as adjusting the length of the control rod but it might also be too much end float on any or all of the three shafts. Check that the selector dogs are .sitting central between the gears when in neutral
Hi theo,
I had the same problem with my box, the bike had sat untouched for at least 30 years ,I found a selector had stuck,managed to get it all free in the bike but,when I road it,found most times I couldn't select third and would also jump out. like matt & douglas say check all the obvious , but in my case when I was overhauling it I found a 2nd & 3rd dog not central,it was then I realised heaps of endfoat on mainshaft and finally worked out there was a missing spacer which through trial & error machined up.Smooth as silk now. Research this sight I seem to remember an exploded view showing this.
