BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: robin smith on 05 September, 2017, 09:05:38

Title: Super Rocket ignition timing
Post by: robin smith on 05 September, 2017, 09:05:38
I was recently in discussion with a well-known magneto restorer on the subject of Super Rocket ignition timing. He suggest 3/8 or even 7/16 BTDC would be possibly more appropriate with modern fuel, as apposed to the 5/16normally applied by myself.

I would be interested to know your views regarding this subject  
Title: Re: Super Rocket ignition timing
Post by: STAR TWIN on 05 September, 2017, 10:19:18
3/8" is the book setting. However, modern fuels are lower octane (they even changed the method of calculating octane ratings possibly to disguise the drop) so I would suggest 5/16" would be more appropriate. The one thing you should avoid is over-advancing the ignition timing. That way pinking and detonation lie. Don't know why you were advised 7/16". Seems quite wrong to me.
Title: Re: Super Rocket ignition timing
Post by: JulianS on 05 September, 2017, 13:17:44
I use 34 degrees BTDC on the most advanced cylinder with high comp pistons. Other cylinder is 33 degrees BTDC. Runs and starts fine on  that.