Gearbox leak

[Expat]

Hi All, I did search for any clues without much luck so am am asking nicely for any suggestions. While the bike has been waiting patiently for me to reassemble the engine, the gearbox has lost a load of oil into the drip tray underneath, level has gone down 1-2 inches probably. Can’t see any obvious places that are dripping when peering underneath at the oil and road dirt mess plastered all over.
Any suggestions as to likely culprit areas/places that would own up to this?

TIA Steve

[G3L1946]

Hi,

I presume we are talking about a B52 gearbox? I've had a few leak issues with the main two being the outer kickstart case gasket (needed replacing and some blue sealant for good measure ) and the drain plug. The drain plug washer appeared fine until I cleaned it up and placed it on a known flat surface. It had become slightly concave and also bore a few score marks. Replaced, and again, a bit of blue sealant for good measure. Plug stopped leaking as did gasket ( well, almost!). Apart from the main gasket and filler plug plus kickstart and gear shift seals that's about all I can offer up!

All the best.
Steve

[SPRIDDLER]

I presume we are talking about a B52 gearbox?

Expat Steve's Profile shows as a 1960 G3LS so most likely to be an AMC 'box but I guess the drain plug can leak on those too.

Can’t see any obvious places that are dripping when peering underneath at the oil and road dirt mess plastered all over.

Well, assuming that it's not one of the g/box casting gaskets leaking there are only 3 holes (k/start, gear lever, mainshaft) so you'll have to clean it off in order to spot which one's leaking.

[G3L1946]

Hi Spriddler,

Must make a note of profiles in the future! I think a good clean up of the road dirt and crud to reveal a clean surface would be of great benefit. Like you say, there ain’t too many places it can leak from. Unless, of course, there’s a crack or damage to the case under the crud?

Steve

[Groily]

If the leak is worse when the bike's parked on the sidestand, my money's on the mainshaft seal. You can lose a lot out of there (DAMHIK!)
Leaks the other side are usually easier to put your finger on (in?)

[Expat]

Thanks for all the suggestions chaps. Yes, it’s an AMC box and the bike has been stood upright in the shed leaning against the wall for months while I sorted out getting a new piston from club shop and a +0.020 rebore and honing done here. I noticed the drip tray was slowly filling up and assumed the oil was from a known crankcase leak. On closer inspection I realized the oil was clean looking, so shock and surprise when I removed the g box cap for a look see and oil level was well over an inch low.
Will follow advice and clean up underneath and check out drain plug etc.
Thanks again.
Steve

[SPRIDDLER]

....... when I removed the g box cap....oil level was well over an inch low.

Are you over-filling it?
It only needs 1 pint. Top up to the level plug (item 87 in the illustration below) and not to the filling hole .
See pages 60 and 64 in the workshop manual here:

http://archives.jampot.dk/book/Workshop ... .NEILL.pdf

Gearbox AMC fill level.JPG

[Expat]

Spriddler, my mistake in not making my observation clearer. Should have added …..’below the level plug hole as seen through the filling hole.’

Thanks for checking though.

[Steve]

still better than my mistake took it out for its second run yesterday, after dropping it in a car park tried to kick it over whilst on the side stand the side stand folded itself back up during the kick and over it went taking me with it, however I managed a rather graceful forward roll picked it up and straddled the bike started it up and drove off. bent clutch leaver aside all was well, but I digress when home I thought I must check the gearbox oil got a 20 ml syringe and put it and I lost count of how many times I filled it but Nev's pint is probably not far off what I put in. I expect it will breath a huge sigh of relief on its next run. needless to say I must have drained it when I took it out but forgot I had just need to hope I've not done to much damage

[1608]

Forward roll? a few press-ups is de rigueur I believe when one takes a tumble in public. If you are going to the rally, have a good run.
Checked my 18s over and found the g/box deficient of approx 1/3 of a pint. Due to a drive side seal I believe.