Gear box Main shaft play (2011)

Hi guys, I am all new to this forum but I have spent a lot of time reading the various posts and realized that if you need som help this is the place to go.

Hopefully someone on this forum can give me hand

I am putting my 1969 Commando back on the road after after 32 years in the shed. I knew it was going to be a daunting task, but I never expected that virtually every item on the bike would require a fair amount of TLC.

From what I can recall from my last ride, 32 years ago, the gearbox was OK and no real problems. Looking at it today there is a play of approximatly 1 mm (0.5 mm in each direction) between the main shaft and the sleve gear shaft (where the gear box sprocket resides).

I assume that it is the sleve gear bushes that are worn.

I can feel no play at all between the sleve gear bush and the oil seal.



Is 1 mm play acceptable? If I can avoid pulling the gearbox apart, that of course would be a bonus.

Also, as can be seen from the picture, the five outer threads on the mainshaft are worn down to about 50% of their original depth. The remaining threads are OK. Is this a cause for concern?

I am afraid that there will be many more questions to follow as the restoration progresses.

Dick in Gothenburg, Sweden

It has got to be the sleeve gear bushes, I'm pretty sure your gearbox will only have two fitted and it might be benificial to fit three. On early gearboxes the bushes can migrate, only the Mk3 has retaining clips. While you're in there you should check the whole lot out.

Cash

Undoubtedly your sleeve bushings are worn. There should be no perceptible play in the direction you are showing. I wouldn't mess with it, break it down and put 3 bushings in place of the 2, you can use bearing retainer on the bushings to help hold them in place. You can also put a washer between the circlip and the bushing to keep the bushing from moving out and being eaten by the circlip. My outer bushing had been eaten in only 13K miles.



Here is a bulletin I found on the washer.

"Sleeve gear bushes are always coming loose-sometimes the outer bush moves inwards to the centre of
the sleeve gear-then all you need do is to Loctite a new bush in the end. Leave the old one in and it will
prevent the new one moving inwards, i.e. fit three bushes in your 750 a la 850. Sometimes the bush
moves outwards and gradually mills itself away on the sharp edges of the circlip which locates the clutch.
That’s worse because eventually the bush disappears completely and all the pull of the back chain comes
on the sleeve gear bearing. No wonder the bearings come loose. Often the first sign of sleeve gear
bushes going -is striking "gold" in gearbox or primary drive oil, watch it! Here the answer is to buy two
new bushes and a clutch location shim (060894 or 060895). Push both bushes-Loctited on the outside--
into the sleeve gear--the middle one stops the outer from moving in-and then put the shim loose on the
shaft to avoid the bush wearing on the circlip even if it does move. It is an advantage to grind the outer
edge of the shim so it will pass through the hole in the primary case (or file or even clip it away with tinsnips to about half the radial thickness)."

There was also a recent thread on someone that did away with the circlip by using shims I think, I never did quite understand it.

While you're there replace the layshaft bearing with a new superblend type.

BTW those bushings are not an exact replacement, you will have to have them fitted (read reamed) to size.

Dave
69S

I'm the guy who jams the clutch center onto the grooves and lands of the mainshaft without the circlip--like a Dominator mainshaft that has no circlip. Looking at the photo above, the clutch center comes to rest just masking the circlip groove. You may have to relieve the inner taper of the engine sprocket a tad to move the whole primary inboard a millimeter or so.


Tim Kraakevik
kraakevik@voyager.net
Three Commandos

i'll bet ya a rear tire no locktite will hold the bushes in place more than a ride or two. The 3rd middle bush is all that's needed and about only thing to keep load bearing bushes wide as possible. Its hard to get thick gear lube into these highly loaded fast spining area in lower gears. So if really wring Cdo neck out in lower gears I highly recommend thinner lube like ATF.

I like the shim idea having seen my outward bush chewed as DogT's in two Combats.

Will have to look into the san clutch circlip mounting as that moves loads closer
to the shaft support and relieves some the risky compromise of nipping up clutch nut not to come off or distort the circlip. Chain alignment is my mystery to do so.

cash said:

It has got to be the sleeve gear bushes, I'm pretty sure your gearbox will only have two fitted and it might be benificial to fit three. On early gearboxes the bushes can migrate, only the Mk3 has retaining clips. While you're in there you should check the whole lot out.

Cash

Click to expand...

Cash, any idea how to remove the retaining clips? There is one on each end of the inner sleeve. They are a blind fit with no way to pick them out. I have alweays found this a problem when trying to remove the sleeve gear bushes.

Thanks

be aware, prior post in this thread was 2011

Norton said:

Cash, any idea how to remove the retaining clips? There is one on each end of the inner sleeve. They are a blind fit with no way to pick them out. I have alweays found this a problem when trying to remove the sleeve gear bushes.

Thanks

Click to expand...

"be aware, prior post in this thread was 2011" right 84ok
George you should start a new thread but...
Mick Hemmings Gearbox Video showed him struggling with a jewelers screwdriver then resorting to a Dremel and ball stone bit to grind a small indent in the center of the grove of the retaining clip, just deep enough to pick up the clip from underneath. If you pick up the video from the INOA it gives it to you. Talk to one of your members in your oNe chapter and they might even have it for you to borrow.
Cheers,
Thomas

Grief! it is a while ago. I think I've only removed these clips once or twice and cannot remember having any difficulties. If it had of been a problem I'm sure I would have remembered.
The only thing that comes to mind is; Try filling a tooth in to the side of an old screwdriver blade wide enough to fit into the groove. You might be able leaver out one side of the clip by dropping the tooth between the clip gap into the groove and twisting the screwdriver.
Dave