AJS & Matchless Owners Club

I am a relative new owner of an AJS 18CS from 57 (shortstroke) and just want to check the ingition timing , valve clearance ect..

The book covering all models (1957 -1954) shows that fully advanced should be 8,9 mm before TDC
In another book covering Competition models shows that fully advanced should be 12,7 mm before TDC for all models - both the 500 and the smaller 350 as well all trial models.

Another thing is that the fuel of today is different than back in the fifties and that could also have an impact

Any advice for best setting ?

Per

Hi - After some reading here and there it seems that 7/16 (11 mm) before TDC / fully advanced would be a fair choice.

BR Per

7/16 BTDC (fully adv) works for me (not competition) and saves your leg a little when starting.


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7/16 doesn't work on my 56 G80CS, pinks like buggery!!!! I've set it to 8.5mm BTDC and still it pinks even on superunleaded fuel. I play with the advance retard to keep it under control. On the 350 56 CS 7/16 BTDC is spot on.

ajscomboman wrote: I've set it to 8.5mm BTDC and still it pinks even on superunleaded fuel.

Most tech data timing settings are just a starting point. Allowance must also be made for the weight of the rider.

SPRIDDLER wrote:

ajscomboman wrote: I've set it to 8.5mm BTDC and still it pinks even on superunleaded fuel.

Most tech data timing settings are just a starting point. Allowance must also be made for the weight of the rider.

And your point is?????

And your point is?????

Perhaps the point of balance has changed over the years!

ajscomboman wrote:

SPRIDDLER wrote:

ajscomboman wrote: I've set it to 8.5mm BTDC and still it pinks even on superunleaded fuel.

Most tech data timing settings are just a starting point. Allowance must also be made for the weight of the rider.

And your point is?????

To clarify..........

With automatic advance/retard the ignition timing won't advance until the engine revs increase, therefore the amount of advance is always matched to engine speed.

However, with manual advance/retard it is customary to fully advance the timing as soon as the engine has started. Hence when the throttle is opened from a low engine speed the engine will tend to labour over-advanced (pinking) until the engine accelerates the inertia of the total bike weight to an engine speed more suited to full advance.

It has been my long-held opinion that Owner's Manuals should have two columns for ignition timing in the same way that they are given for tyre pressures: One column giving recommended settings for riders up to 20 stone and a second one for the rather less lithe Fray Bentos and Ginsters Peppered Steak pie eaters.

clive wrote:And your point is?????

Perhaps the point of balance has changed over the years!

May be the conrods have got shorter and the piston has got larger

My G80cs runs great on 7/16" BTDC scares the life out of me

Colin