There was a discussion about this in the past, but it may have been lost in the purge of old posts, so apologies for treading on well-worn "timing" territory...

Anyway, my 1946 civy is running really well finally, and with a new regulator coming it'll be in great running shape. Video to come someday soon. One question though. At idle, the engine hesitates and sometimes stalls when timing is fully (I mean fully!) advanced. Idle speed and mixture seem spot-on, and the idle is nice (if not a bit fast perhaps) with VERY slightly retarded timing, and idle will also hold to a nice slow thump with a bit more retarding. Under more throttle, the bike runs pretty much the same when fully advanced, or very slightly retarded (i.e., when retarded to help the idle).

So, is the rough idle at full advance acceptable and/or normal? Or should I check timing... again. Thanks!

Craig

Hi Craig..The bike is not really designed to run full advance at idle..in fact slow running adjustments should be made with the timing set slightly retarded.
Take a look at the 'technical section' on ignition timing that explains the theory behind it...Ian

email (option): ian@wright52.plus.com

Ahh yes, thanks Ian! I knew the discussion was familiar, but I admittedly forgot to check the technical section. Much thanks, sounds like I'm well within the range of expected performance. Good news!

Craig

On bikes with an auto advance/retard controlled but bob weights on springs, it doesn't advance until it's doing a few thousand revs. So at idle it's fully retarded automatically.

email (option): horror@blueyonder.co.uk

Auto advance units will return the timing to their own 'fully retarded' position, though this position will differ from engine to engine as they have varying degrees of 'retard'. There is no theoretical 'fully retarded' position.
Typically it is around 12- 15 degrees with auto units. The advance retard facility on a manual system covers a wider range and this must be considered when making adjustments or setting up for starting. An M20, for instance, may well not start at all if you attempt it with the lever set in the fully retarded position, as it will be firing well past TDC...Ian

email (option): ian@wright52.plus.com