9:1 pistons

[Erico]

Hello....has anyone fitted 9:1 pistons to an A10 with auto advance and retard. I've heard that you need to junk the auto unit and fit a manual advance and retard set up to deal with the compression fuel etc. I don't want it pinking and knocking. Thanks Erico

[bsa-bill]

I don't want it pinking and knocking.

Shouldn't of fitted 9:1 piston then 

Yes a manual advance would be help in that respect on hills or acceleration , although the A/R unit I think only retards at very low revs so I bet someone has left it on and just timed the bike accordingly

[muskrat]

Yes I found the AR unit advanced a bit too quick for high comp. Retarding it enough to stop the pinging meant it wouldn't pull the skin off a banana!! I was in the process of removing weight off the bob weights to slow it down when I ditched the magie and went electronic. A little better but not perfect. My solution is if it pings throw it back a gear and rev it.
A manual advance magie would be better for normal road work. (Normal isn't one of my riding styles  )
Cheers

[wilko]

Stronger springs in the advance unit should slow the advance characteristics.

[muskrat]

That's right wilko, but it's hard enough finding good std ones down here, let alone ones a few oz heavier.
Cheers

[wilko]

Got any old car dizzies you could compare with lying around? Springs I mean.