Manual Advance/Retard . trivial query .

[Taid]

The instruction manual for my, newly acquired, 1959 M31 de Luxe, in the Info page on Controls, says retard 2/5 of movement to start. The M31 deluxe start-up section says retard 1/8 inch, which doesn't seem a great amount.

I have never before had a manual advance/retard bike and having no great wish to be launched into space, I must ask, which of these is correct?

Also, should I go to fully advanced as soon as started, or give time for it to establish tickover?

Thanks

[1608]

There is no exact setting, you need to experiment to find the most consistent setting for your bike. Once started you can adjust the a/r lever to find the smoothest running and then when riding leave it to fully advanced

[Taid]

Thank you ..

I'll see how things go ..

T

[Groily]

It is worth noting that the magneto works at its best at full advance and that retarding manually weakens the spark (just what we need for starting, of course!)

The engine may run slightly better on modern fuels with the basic setting a fraction retarded from 'book' - but the magneto wants to be able to do its business at the best moment for it internally. The 'best moment' is when the points open just after the 'flip' of the armature (which you can't feel when things are connected, but which very is obvious when the thing is on the bench).

Usually, I give twins about one third to a half retard for starting, but they are pretty easy compared to singles and seldom want to break an ankle (if not highly tuned) even if left advanced.
The engine should be close to full advance by about 2000-2500 rpm (which is how the automatic advance systems are broadly designed) - so it's a revs thing as to what setting is best. Very low rpm = retard is fine, hot or cold. High revs need the advance or the bike will run very flat, may overheat, and won't be much fun to ride!

There is more to be said than we sometimes care to admit for the auto-advance units used in conjunction with, eg SR1 mags on singles. It's a shame there was never - AFAIK - a factory-made timing gear that would accept an ATD and still fit under the timing cover of most of our twins (which is what most models of those lesser marques beginning with B, T and N went for).

[Taid]

Thanks, G ..

Very informative .. whether I'll remember is another matter ..

You've saved me searching for an auto a/r magneto replacement, anyway ..

I've just got a new end cap with an earthing contact, so I can link it to an antisumping tap/switch..