Norton Commando 850 MKIII Service and Recommissioning. Part 15: Starter Motor Problem Sorted

[@jjrider6758]

Could it be the lack of thin enough lubrication due to the fitting of the belt drive, resulting in there being none of the recommended ATF fluid in the Primary casing ?... I only say this because I used to manufacture specialist hand-cranked food processing machines (pasta rollers !..) which had a one way 'clutch' with three rollers (simpler design, but similar in principal to the MK3's Sprag clutch) - Some owners/users would send them back for repair because this clutch had ceased to function and invariably it was because they had used grease on the clutch rollers as part of their routine servicing. This was far too thick or sticky in consistency (a thin coating of sewing machine oil being required..) and prevented the rollers from rolling up and/or down the slope of the clutch centre to either engage or disengage the drive. Once the grease was removed and the unit correctly lubricated it always worked perfectly.

[@Chris.rooke150]

Thanks for the info. The use of grease in this instance certainly seems to have caused the problem. The sprag bearing must have worked okay initially with the grease to some extent, but possibly only when it was new. Now that the grease is older (and colder/thicker?) it was definitely causing the bearing to slip. I used a combination of WD40 and lithium spray grease on it and it immediately felt different/correct. I'm hoping that form of lubrication is okay.🤞🤞🤞

[@TornadoCAN99]

Might also be affected by heat build up within the un-vented primary casing. That belt will make quite a bit of heat as it runs. Grease will age faster and gum things up. Many belt drive conversions on bikes add air vents into the casing or even fully remove the outer casing...but those are not Nortons running starter mechanisms.

[@dalereed2626]

Well done Chris.

[@Chris.rooke150]

Thanks, Dale, that was a bit of a mystery, but very happy now that it's sorted. 👍