AJS & Matchless Owners Club

Maybe I could fit two, and then a third over the top and once the mag is bolted in place sort of push the third one down between the two to apply some pressure? That make sense?

Apply pressure and the case could deform or something else comes under undue pressure and creates a problem in the long run. My mistake, back in the day, was not to play sufficient attention to the straightness of the chain run between the camwheel sprocket and the mag sprocket.

Personally, I think Pharisee's solution is best, foam, just to prevent water ingress. Maybe with some high melting point grease on the inside wouldn't do any harm?

Johnny B

For anyone thinking about going to oring route in the future, I have fitted two on the 'stub' and then a third over these, sort of sitting in the trough between them. Once my magneto is in place and staying there I'll push the third oring down a bit which should squidge the second one out and against the chaincase just right.

I was looking at a SR1 mag the other day and the seal compressed to 0.5" between case and Mag body

That sounds a bigger gap than normal. The correct thickness for the SR1 rubber should be 0.47", which ours (AMC Classic Spares) are, though someone mentioned in a previous post that it wouldn't compress enough. That may be due to modern rubber being less squishy than the old stuff but in my position it's very hard to compensate for that when commissioning a part for manufacture.

Ill tell Ray his bike is wrong , or perhaps not it was measured in the garage with a 2 foot steel rule !