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Oil in primary chaincase

Hi everyone
So I have an oil leak that`s annoying me. It chucks oil over the back tyre. Its not from the crankcase breather . In an attempt to find it. I drained the oil out of primary chaincase cleaned it and went for ride. So after about 30 miles there is oil back in the primary chaincase. Am I right in thinking oil seal on gearbox. The gearbox is a later M21 gearbox I believe so would the oil seal be the same as the WM20 and can it be replaced without totally removing the gearbox.
Additionally my clutch is a Triumph 4 spring conversion so any idea what tool I need to remove/compress it.

Cheers Colin

email (option): colinmbrindley@btinternet.com

Re: Oil in primary chaincase

The later M21 gearbox has a modern lipped oil seal which runs on the shoulder on the back of the gearbox sprocket...They are generally pretty reliable and long lasting and even if it was worn it would be more likely to leak onto the floor rather than into the chain case..The WD gearbox has no seal in the modern sense....If oil is just appearing in the chain case it could be coming through the main bearings from the crank case..Is your engine more 'leaky' than normal? (from other places...)...

It may be that the crank case breather is not functioning and the crank cases are being pressurised...That can force oil through the bearings into the cases but there will frequently be leaks in other places as well...

Another possibility is that the sleeve gear(top gear) bushes are worn and the gearbox is leaking there..That might find its way into the casing...If those bushes are gone there will be vertical 'lift' present if you get hold of the clutch and attempt to move it up and down...There should be barely perceptible free play in the bush. To remove the Triumph type clutch main shaft adapter (the clutch is mounted on the adapter) used when a Triumph clutch is fitted you will need the correct puller...This is used to get the adapter off the main shaft...Available from many Triumph dealers (not the modern ones!!) and other British bike shops...Probably on the internet also..

I'd start with checking the crank case breather function as it's the easiest one to look at...

I've never tried to fit an oil seal with the box in place...I think it's theoretically possible once the clutch, inner primary chain case and gearbox sprockets are removed if you can manage to prise the old one out of the case...

Has this problem suddenly appeared?...Ian

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

Re: Oil in primary chaincase

Thanks for the reply Ian.
The crankcase breather leaves a small amount of oil on the floor after a run so I assume its working but I will take it off and have look first. No leaks from anywhere else.
I know this sounds daft but I am pretty sure its gearbox oil because of the colour. The gearbox oil is golden in colour and looks likes brand new, which it probably is as I think it was rebuilt 300 miles ago along with the engine. However the engine oil is much darker, I have just whipped the engine sprocket off and its bone dry under there. I think I will strip the clutch further and investigate later. Ive only put about 200 miles on it since I bought it in January but its been throwing oil out whilst Ive been riding it. Hence I wish to try and cure it before it starts covering the MRS in oil when shes sat on the pillion seat.

email (option): colinmbrindley@btinternet.com

Re: Oil in primary chaincase

Has it been wet sumping while it's been stood?...If it has there will be more oil in the crank case than the return pump can cope with when you start it initially and it will come out through the breather until the crank case is cleared..Ian

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

Re: Oil in primary chaincase

I don’t think it’s wet sumping but I’ve not checked. I will tonight after work.

Re: Oil in primary chaincase

I've found there can be wide variations in how long it takes for a meaningful amount of oil to get to the crank case due to wet sumping...Some engines will do it over an extremely short period, just a couple of days, others can take weeks or even months...

How long is your bike standing for under normal circumstances?...Ian

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

Re: Oil in primary chaincase

It can be a week before I get chance to go for a ride. Weathers been good though so I’ve managed a few trundles around recently.

Re: Oil in primary chaincase

About a table spoon full just drained out of the sump, is this Ok after 3 days ?

email (option): colinmbrindley@btinternet.com

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