AJS & Matchless Owners Club

Look Ma, no leaks!
(well, nothing more than is normal, anyway...) The gearbox rebuild seems to have worked: gear selection is sweet and the oil seems to have stayed in. So all good for now.
Thanks everyone for all the help and advice!

Next up: full engine rebuild to deal with a rather loose-sounding main bearing. Hopefully it'll hang on until winter...

clanger9 wrote:Hi Steve,
You don't want to put an o-ring there. As far as I can tell, it goes in the recess between the outer case and the bronze bush:
Some people fit another o-ring between the two bronze bushes to improve the seal.

clanger9 is correct in stating where the oil seal goes but still be prepared for a slight leak as replacing the seals often does not work as well as you would expect it to. I had a problem with leakage from my kick start shaft seal, it still leaked even after fitting the modified seal. I ended up fitting two seals in there, it made the kick start return a bit sluggish to start but it soon freed up and no leaks

Well after 7 months and loads of brilliant advice from this forum I've finally got the box back together!

Clanger's guide is extremely helpful as was Ozmadman's knowledge of every small detail.

I started without much confidence but ended with a sense of achievement.

Learning points are covered in this thread and others, but to list a few;

Parts are available from club spares, AMC Spares, Russell Motors and Andrew Engineering (who found a supply of the elusive sliding gear with undercut dogs) but also Norvil Engineering who had the main output gear.

My box, like many others I suspect, had not been re-built with much care and everything had to be double checked eg missing washers, the clutch body peg etc.

The revised output gear had been mismatched with the old peg type sliding gear which led to jumping out of top.

Ozmadman's re-assembly method works really well; when I finally came to put in the gaskets and put it together it went first attempt, although I had practised several times without the gaskets.

Thank you all once again, Steve S.

Congratulations and well done, Steve! There's a real sense of achievement in getting something like this working again. It looks line another Lightweight is well on the way.

I hope the rest of the rebuild goes well and you're back on the road before too long...

And the same from me as well. I was a complete novice back at the end of 2011 when I acquired my lightweight having been out of the motorcycle scene for the previous 39 years. I knew nothing of these bikes at all but a few years later having stripped the bike completely, rebuilding not just the gearbox but also the engine and forks (they were bent), rear swing arm, front and rear hubs and a complete D.I.Y repaint job (don't ask me anything about wiring though!) There is not much (apart from the electrics) that I don't know about these wonderful underrated machines. You learn from your cock ups and mistakes but it's this where you can help others. BTW, like the pic of the box on your bench but don't forget to bend over that tab washer behind the large nut if you haven't done so already !! AND.. clanger9's gearbox rebuild instruction manual is a real gem, maybe more of us could use this facility to document our projects for the benefit of others

Hi clanger9, Great write up! Very well done
After reading this I have now decided to try to repair my own gearbox.
My bike (G5) was pushed into the dark corner at the back of the garage two years ago because it kept jumping out of top gear and spewing gearbox oil over the floor.
I have sourced all parts needed except for the main gear bearing oil seal part No.041267 (I did order an oil seal part No.041267 from Norvil but it has thicker shoulder causing drive sprocket to tighten up against it locking the output shaft)
Can I ask if you replaced this seal and if so where did you obtain it from?
Have tried club spares, (no stock) & emailed Russells but got no reply.

Hi Colin,

Glad to hear the guide is useful! I didn't replace the seal in mine, because it was in good order (and the spares scheme don't have any).
Interesting to know that the Norvil seal doesn't fit, especially as it's the same part number. I presume you've tapped it all the way home?

It's probably a waste of time emailing Russells - they never reply. They are very old-school: you need to ring them up (on the one phone line - always engaged!) and speak to Les. He is super helpful and will probably need to go and "check in the warehouse" to see if they have any. Hopefully he'll be able to sort you out...

PS: if you are stuck, perhaps this one will fit? http://villiersservices.co.uk/index.php ... cts_id=764

Yes I tapped the seal through until the back of it was tight against the bearing, the face was still flush with the outside lip of the gearbox which meant that the inside tapered edge of the drive sprocket was resting against the face of the seal.
When I tightened the sprocket retaining nut, it caused the sprocket to press into the oil seals face locking the output shaft solid.
Thanks for the link for the villiers parts, I never even thought of them.
I have ordered that oil seal and will report back on whether or not it fits.

Hi, sounds like an incorrect size seal. It should tap into the casing and sit about 4 mm in, thus allowing the sprocket to clear it. I got my replacement from Les at Russell Motors.

Steve S.

colinlinden wrote:Hi clanger9, Great write up! Very well done
After reading this I have now decided to try to repair my own gearbox.
My bike (G5) was pushed into the dark corner at the back of the garage two years ago because it kept jumping out of top gear and spewing gearbox oil over the floor.

This is an excerpt from the workshop manual that you may find useful.. right click on the picture then click "view image" to get a larger view