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M20 gearbox sprocket

This is my first time changing the gearbox sprocket on my 1945 M20. The old one is worn with pointed teeth and it slipped easily off of the output shaft. When installing the new one, it is very tight and barely exposes the first thread of the shaft and won't travel further onto the shaft. I bought this from Les at Russell Motors and certainly trust him. Do I need to 'rubber mallet' it on?

Thank you in advance.

Scott D

Re: M20 gearbox sprocket

Personally I would try and relieve the splines in the sprocket a bit, maybe with a tiny stone in a Dremel or something. I expect a file will just slide off. Ron

email (option): ronpier@talk21.com

Re: M20 gearbox sprocket

Scott D
This is my first time changing the gearbox sprocket on my 1945 M20. The old one is worn with pointed teeth and it slipped easily off of the output shaft. When installing the new one, it is very tight and barely exposes the first thread of the shaft and won't travel further onto the shaft. I bought this from Les at Russell Motors and certainly trust him. Do I need to 'rubber mallet' it on?

Thank you in advance.

Scott D
What ever you do resist hitting the sprocket with anything
Ultimately the force goes to the bearing retaining lip on the inner cover which breaks off very easily .
Check the sides of the spline grooves
Some are cut square and some are cut at an angle so they converge at the center of the circle .
The latter is the correct way o cut a spline but the former is the cheaper way
The last time I replaced one it tool a week with a diamond sharpening stone and bearing blue to make it fit properly ( well go on at least ). Unless Les supplied you one still in WW wappings then there is a 99% chance it is an aftermarket job and unledd he went to the effort might actually be unaware that his supplier has supplied him a dud batch
Also check that there is not a burr raised on the driven face of the sleeve gear
It does not take much of a burr there to stop the sprocket going on.

email (option): bsansw1@tpg.com.au

Re: M20 gearbox sprocket

Thank you Ron and Trevor. I've got some work to do this next week!!

Regards, Scott

Re: M20 gearbox sprocket

Found the issue. The outer diameter of the section of the cog that fits into the gearbox is 1 mm larger diameter than the old one. Any recommendations on a source for a NOS cog?

Scott

Re: M20 gearbox sprocket

I remember having a similar problem but I had another sprocket so didn't follow up on the problem.

I think it may have something to do with the later boxes having oil seals and the sprocket may be for one of those boxes.
Anyone with more knowledge out there?

If you have a lathe with soft jaws you could turn it down to size.

Cheers
Pete

Re: M20 gearbox sprocket

I may have a suitable sprocket...I'll take a look tomorrow...Are you fitting the standard number of teeth?...

Mail me off forum this evening to remind me...I'm in that age group!!:laughing: ....Ian

email (option): ian@wright52.plus.com

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