Disturbed Gearbox leaking onto Drive Chain

[bbenxe]

Replaced a kickstart return spring today using some very useful advice from elsewhere on this forum having broken it greenlaning on the Fosse Way. See below for an action shot and then necessary zip tie to stop it flopping down.

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However having spent the afternoon blatting around Bristol I got home to find lots of oil spilling out from where the drive chain exits the engine cases and then spraying onto the rear wheel in such large quantities that I was surprised I hadn't felt it slip while out.

Would knocking around on the right side of the gearbox have disturbed something on the left to cause this new leak...? Otherwise what's the likely leaking join that's the source so I can order the necessary gaskets/seals before my first chance to have a deeper look next weekend.

Thanks in advance!

[clanger9 Profile]

Mine pees oil out of the chain side - it seems to come from worn sleeve gear bushes.
There's no seal, the design just seems to rely on a close fit of the bushes...

[Janet Profile]

There is an oil seal for the main drive gearbox bearing, part number 041267. Obviously I'm no expert although I do have a vast experience of oil leaks ( as several people will be able to confirm) but if the leak has suddenly happened I'd suspect that as the culprit because of it being just a thin bit of rubbery material. My view is that it would be more susceptible than the metal bushes to a little bit of movement caused when you've pulled of the other end of the gearbox.

[clanger9 Profile]

Yes, Janet's right: there is a seal (around the output shaft). That's more likely to have failed suddenly.
However, there's no seal between the input & output shaft. That's where mine leaks from...

By the way bbenxe, I just noticed your nifty rear suspension units. Those really look the part on a scrambler. Where did you get them and do they fit OK? It'd be good to know, because original Lightweight shocks are like hen's teeth...

[bbenxe]

By the way bbenxe, I just noticed your nifty rear suspension units. Those really look the part on a scrambler. Where did you get them and do they fit OK? It'd be good to know, because original Lightweight shocks are like hen's teeth...

I actually followed your advice from a previous thread viewtopic.php?f=15&t=18002&p=163366#p163366

They're the 390mm Betor MX shocks from Bike revival. Standard G2 is 380mm, G2 CS is 400mm so I went for a happy compromise.

The shocks are excellent, massively improved the handling on road, and have taken a serious beating off road as well where I was constantly impressed at how well this little old bike was handling the terrain.

They came with steel bushes that were too long for the studs on the frame so I had to push these out and replace with shorter ones, but advice over the phone from Bike Revival was excellent, and they were delivered very quickly too!

The only failing is that the bike sits at quite an alarming angle on the side-stand now so am investigating lengthening it to compensate....

[clanger9 Profile]

It's great to know that they fit OK (and that Bike Revival were helpful!). Lightweights are especially tricky because of the unusually long shock absorber stem.
In the end my original shocks turned out to be fine, but those Betor units will be an excellent option for CS owners.

[Ozmadman Profile]

There is an oil seal for the main drive gearbox bearing, part number 041267. Obviously I'm no expert although I do have a vast experience of oil leaks ( as several people will be able to confirm) but if the leak has suddenly happened I'd suspect that as the culprit because of it being just a thin bit of rubbery material. My view is that it would be more susceptible than the metal bushes to a little bit of movement caused when you've pulled of the other end of the gearbox.

Don't run it unless you have the gearbox oil topped up to the max otherwise you will knacker the box!!

[bbenxe]

There is an oil seal for the main drive gearbox bearing, part number 041267. Obviously I'm no expert although I do have a vast experience of oil leaks ( as several people will be able to confirm) but if the leak has suddenly happened I'd suspect that as the culprit because of it being just a thin bit of rubbery material. My view is that it would be more susceptible than the metal bushes to a little bit of movement caused when you've pulled of the other end of the gearbox.

Thanks Janet, that does indeed seem likely.

I've located 041267 on the exploded diagram, and think I've located it in the workshop text referred to as "the oil seal with metal side facing outwards" but can't identify whether it can be replaced from outside the gearbox or whether it requires all the internals to come out... Any idea?

I haven't gone into a gearbox before so would prefer the former although I do have some friendly local section members that might be able to help.

[Janet Profile]

I've located 041267 on the exploded diagram, and think I've located it in the workshop text referred to as "the oil seal with metal side facing outwards" but can't identify whether it can be replaced from outside the gearbox or whether it requires all the internals to come out... Any idea?

It goes in from the outside.

[bbenxe]

Thanks Janet.

For reference, no stock of this part 041267 the gearbox main seal is held by the parts service, AMC Classics, or Andrew Engineering, but is carried by Norvil as the Norton lightweights shared the gearbox internals with the AMC lightweights for a period.