Timing side crankcase evolution

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APRRSV

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Can anyone tell me at what serial #, approx., the timing side crankcase evolved from having a bolt on plate covering the distributor hole at the rear of the timing chest to the type that had no hole to cover?

Thanks,
Ed
 
The hole (with cover plate) was intended for an electric starter motor, not to blank off the 20M3 "distributor" (points housing) hole, as the case went from points housing (20M3) to 'solid' for the early 20M3S models.
The hole intended for the starter motor (with the cover plate as the electric starter was never fitted) is supposed to have been introduced at either 136618 or 133618 depending on the source of the information, so around mid-70, this continued until around mid-72 when it became a 'solid' are again.
 
L.A.B. said:
The hole (with cover plate) was intended for an electric starter motor, not to blank off the 20M3 "distributor" (points housing) hole, as the case went from points housing (20M3) to 'solid' for the early 20M3S models.
The hole intended for the starter motor (with the cover plate as the electric starter was never fitted) is supposed to have been introduced at either 136618 or 133618 depending on the source of the information, so around mid-70, this continued until around mid-72 when it became a 'solid' are again.

I've often wondered why the old magneto space was not utilized for a starter. Seems like it would have been much simpler than all the monkey-motion of the Mk III setup. It would be interesting to see what sort of starter drives/clutches they had planned.
 
Danno said:
Seems like it would have been much simpler than all the monkey-motion of the Mk III setup. It would be interesting to see what sort of starter drives/clutches they had planned.

Timing side crankcase evolution


It appears the original (Lucas then, not Prestolite) starter motor was a total failure, apparently, it had no anti-backfire device incorporated into the drive, the experimental starters would regularly self-destruct when the engine backfired so never did go into production!
 
One of the starters have recently surfaced, sadly the source is unknown, but the person had bought one and inquired why it would not fit a MK3! having assumed it being advertised as Norton Electric start motor would fit.
 
Thanks to all who replied. Do I understand correctly that:

1. Early Commandos (1968 - 1969?) had the hole because they used a distributor (points) at rear of timing chest.

2. Sometime in 1969? until mid 1970, the timing side case was manufactured without a hole.

3. Sometime in late 1970 and until mid 1972 the cases were manufactured with a hole again for a starter motor.

4. Beginning in late 1972 the hole was again eliminated for good.
 
Madnorton said:
One of the starters have recently surfaced, sadly the source is unknown, but the person had bought one and inquired why it would not fit a MK3! having assumed it being advertised as Norton Electric start motor would fit.

Yes, well, those "Norton Commando" (allegedly!) Lucas M3 starter motors surface occasionally although I don't remember seeing one with the drive assembly;
http://www.ebay.co.uk/itm/STARTER-MOTOR ... 2091697979

READS; LUCAS TVS. 26925012A M3. TYPE NO; 26515A 12V. MADE IN INDIA, MAY 1972.
FAR SPARES HAD ONE OF THESE LISTED FOR A NORTON 750 COMMANDO 1971 - 1972 ENGINE BUT YOU MUST BE YOUR OWN EXPERT!!

:roll: :wink: :lol:


I believe the Lucas M3 motors were used for various non-motorcycle applications as well as fitted to the Triumph Tigress/Sunbeam scooter, Velocette Viceroy, Triumph T160 Trident and T140ES, also the Norton ES400 Electra and Norton rotaries, and would have been fitted to the 350cc Triumph Bandit and BSA Fury if had they made it into production, so it could potentially be 'Norton' if not 'Commando' however, given the 1972 production date of that starter I doubt it.
 
L.A.B. said:
It appears the original (Lucas then, not Prestolite) starter motor was a total failure, apparently, it had no anti-backfire device incorporated into the drive, the experimental starters would regularly self-destruct when the engine backfired so never did go into production!

This raises a question about the current Pre MK3 starter systems from Alton and CNW. Do these systems have some sort of anti-backfire device incorporated in the design?

Glen
 
worntorn said:
This raises a question about the current Pre MK3 starter systems from Alton and CNW. Do these systems have some sort of anti-backfire device incorporated in the design?

The Alton has a 'shock absorber' type anti-backfire device although it seems they had problems with the early ones as it wasn't strong enough.

alton-electric-starter-share-your-experience-t13414-60.html#p219421

I expect the CNW kit does too but I don't know it operates.
 
there is a good article about the proposed elec starter that was for those prepared cases in the latest Andover monthly newsletter, worth a quick read.
 
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