AJS & Matchless Owners Club

Hi All,

Does anyone know the correct ignition timing for a 1962 short stroke 350 please?

I have looked in several manuals/books and am getting conflicting results. Fred Neill's books state 1/2" BTDC (and I guess he ought to know, being AMC service manager), but I have seen 7/16" BTDC and also WC Haycraft's last edition (See pic) of AMC Singles book states 11/32" BTDC for 1962 engines, after engine number 41575. My engine number is 41588

It is currently set at 11/32" BTDC but seems a bit 'flat'.

Doubt it makes a difference but the engine is a bit of a bitsa, it has a 1962 M16 short stroke roadster bottom end with a comp alloy barrel and head, it is fitted with a competition (camring) version of the N1 magneto.

Thanks
Peter

P.S. I tried it at 1/2" BTDC and it wasn't great

http://archives.jampot.dk/book/Owners_m ... Manual.pdf
Have a look at this 1962 instruction book, was I seeing things? 1/8" BTDC ? There's also something about making sure points cam goes in correct positions. Also often forgotten, points must be set correct and A/R set fully advanced, before timing. But your bike has N1 mag. bits??

Thanks for your reply Rob.

I think the 1/8" BTDC refers to the fully retarded position. It is currently 11/32" BTDC from fully advanced, which I guess equates to 1/8" fully retarded.

Regards

Peter

Hi Peter

The Lodgemark Press service and overhaul manual for the singles by F.Neill also shows 11/32" (8.73mm) or 34 degrees BTDC on full advance or 1/8" retarded for engines after 41575. I've used these figures on my '63 G3 and when running correctly (long story...) goes very well with excellent acceleration and performance albeit with a different riding style to the long strokes - don't be afraid to rev it.
At first I had problems with over-advancing due to worn bob weights on the A/R unit but this should not be a problem with a magneto.
I have also heard that these engines only run well with the correct cigar shaped silencer as these are absorbion type but for '62 it would have had the normal shaped singles silencer although I don't know what internal baffles these had.

From the Lucas Service Sheet it appears that the N1 can have manual or auto A/R. I'm not clear as to which you have.
http://archives.jampot.dk/technical/Ele ... 2F_KVF.pdf

If yours is auto is it advancing correctly as the engine revs increase? A mag chain that's too tight can inhibit the A/R operation.

If it's manual A/R why not set the timing at 1/2" (i.e. 16/32") BTDC and adjust (retard) it whilst riding for best performance? When established you can check the amount of A/R back in the shed and reset the timing accordingly but with the h/bar lever at full advance rather than backed off as when you ended the test run?
As an afterthought......... I'd use Premium fuel and watch out for pinking whilst running at 1/2" BTDC.

Or, the other way around: if you can't make it pink on regular fuel, it's not advanced enough...

Is it this one that you brought to the Ardingly show?

Thanks for your replies chaps.

The F Neill books I have must be too early James, I look out for a later book.

Yes Nev, that is the bike. I've just been out for a 18 mile run and it still seems a bit sluggish compared with what it was like before the rebuild..... I could just be imagining it I suppose.

Mag has a manual advance/retard, so if it continues to be a problem I'll do as you say Nev and set it at 1/2" BTDC, after the Ardingly show on Sunday.

Peter

To all intents and purposes my 56 CS will be the same as yours Peter and that I've set at 7/16 btdc. It's a revvy little bugger so are you certain the cam timing correct?

just advance it until it nearly breaks your leg on starting by kicking back . then you know its about right ,