It's a difficult one Yannick. The M20 valve lifter is not one of BSA's best designs and can be really fiddly to set up. Sorry I am nowhere near you to help. You need to find an old M20 owner near you to show you some tips.
In the meantime you could disconnect the cable which will mean pushing the piston past the compression stroke with the kick starter, before kicking to start. This is what I am doing with my Royal Enfield CO, since the nipple popped off the cable. It's fairly simple actually. I know it's only a 350 but it does have a high comp piston. Ron
Valve lifter is easy
With the engine at running temperature slip your finger on the valve lister and pull just enough to take all of the slack out of the cable
If you feel a tapping on the lever it is too tight so you go to the front engine bolt that anchors the cable & back it off 1 turn ( easier said than done ) then repeat the above test till when you take the slack off the cable you feel nothing on the lever
For some weird reason people think the vlave lifter has to raise the valve a large amount when in practice a couple of thou is all you need and I find that is better because you can hear the charge whooshing out of the cylinder better
I would not go that far Ron
I don't think I have ever replaced the valve lifter in exactly the same place in 30 years of riding the bike .
Thus I get a lot of practice in adjusing the cable
A current project is to make a front engine bolt with a bigger offset for the valve lifter as the angle on mine fouls on the crank cases
I have found the standard engine plate bolt a little too long on the shank so fit a spacer under the head to prevent the adj. screw touching the crankcases...Ian
Valve lifter is easy
With the engine at running temperature slip your finger on the valve lister and pull just enough to take all of the slack out of the cable
If you feel a tapping on the lever it is too tight so you go to the front engine bolt that anchors the cable & back it off 1 turn ( easier said than done ) then repeat the above test till when you take the slack off the cable you feel nothing on the lever
For some weird reason people think the vlave lifter has to raise the valve a large amount when in practice a couple of thou is all you need and I find that is better because you can hear the charge whooshing out of the cylinder better[/quote]This is a great tip !
