B31 and Lucas Mag

[sidewaysid]

Recently I had a spot of trouble with my Magneto having spent 3 years completing the build of my 1947 BSA B31 it was the big start-up day, but the spark was gone? I eventually had no other choice than to remove the MO1  mag and get it on the bench. It turned out to be the points staying open, I got that all sorted and I was playing with the Mag on the bench whilst reading up on the ignition timing, which is set in the fully advanced position, so looking at the points face on, and the mag runs clockwise, then the cam plate which operates the points opening must be rotated anti-clockwise to make them open sooner (am I correct) and that means pulling the cable, which then means my handlebar lever needs to be pulled towards me sitting on the bike, however, the book and the service sheet seem to say push the lever away? I then thought oh shit I have the wrong Mag, or at least the wrong-handed advance unit? but I went to a bike meeting and there were 2 B31s and they all had the same hand as mine, that is with the cable pull on the right looking at it points in view, am I going stark raving bonkers or what.

[berniej]

Nope, you're right. If the cable enters from the top right then it's 'pull to advance'.

On later mags this was changed so the cable entered on the top left - 'pull ro retard'.
I believe the logic was that if the cable broke, the spring would pull it fully advanced so you could continue riding.

Cheers,
Bernie

[idie]

Not just a broken cable. If the bolt on the lever isn't tight enough it will vibrate back and retard the spark.

[sidewaysid]

Thanks Guys I am not totally mad, well nearly ah ah ah