Crankshaft oil seal - MK 1 Lm

Until being thrashed to Spa last weekend my Mk1 Le Mans has never leaked oil, no nasty black spots on the floor. Sadly this weekend it joined the throng - 4 Mk1s all leaving telltale spots in a side street in Malmedy.When I got home on Sunday night - no leak. Monday morning the ground was clear. Rode to work and home and still no drops.Can crankshaft oil seals repair themselves???Having decided on Sunday afternoon to drop the engine and replace the seal I’m now wondering whether I should or not…

May just be due to the heat or a bit of spirited riding. It could easily leak or blow of through the crank case vent when ridden long or hard.
A more gentle ride to work probably would not get things hot enough to cause a leak.

the breather pipe has a nice emulsion coming out (It’s routed to the rear mudguard).The oil is definitely coming from the little square hole in the bell housing.Re thrashing, the last bit to the tunnel I got an “indicated” 130 (!!) and not a drop on the train…

Was going to suggest gearbox breather, this does tend to blow when doing high speed runs, the air flow often throws the oil along the underside of the box and bell housing to drip from the low point (and your boots sometimes).G.

Further to Duffo’s point check how much gearbox oil you have.I normaly use an Allen key to dip down from the inspection hole.

definitely engine oil - gearbox oils stinksno breather box, tube direct from from breather’s never done it before so something has blown…

REEELAX DO NOT PANIC A breather WILL blow a bit out after being thrashed MORE so if it has “been a while” No they don’t fix themselves BUt a tiny wee bit of oil LOOKS alot more…The breather is doing what it is SUPPOSED to do and allowing the crankase to B R E A T H E so it is inevetable that some oil may get out ESPECIALLY after a good sound thrashing… Heck YOU would be breathing heavily and spitting out stuff had YOU been thrashed like that, why should y bike be different?


If it is not blowing NOW and the oil levels are all good just ride the damn thing NOTHING has “Blown” hell if it has there will be a wee bit to mop up, so what, not worth major surgery for …is it?

I had an engine oil seal blow took 5 goes to get one that worked in between times it went

To Scotland
To the South Coast
The V Twin

At no time did it ever need added oil, BUT after a high speed run there was a blob of oil LOOKED awful but as I say no real differenct in anything other than it looked mucky.

Don’t panic ride it as you usually do IF it does dribble a bit, get a pan in the short term and only if it gets a puddle then rip it apart and do the seals.

Wait till it needs a clutch is what I do nowadays then for the small cost of seals it is well worth doing…HOWEVER as I found out a very thin smear of silicone gasket, high temp stuff saves you haveing to do the job 5 F*****in times

Also one of those green scotchbrite pads as used in the kitchen A NEW ONE GUYS cleans the alloy up a treat to accept the new seals…tip from Guzziology that…(If ONLY I had read it BEFORE the 5th GO)

guzzibear2013-07-09 19:12:10

The answer I was looking for :slight_smile:

We’ve had em drop a bit out the bellhousing before then its gone away, Guy thinks sometimes its just where the crank stops. Remember reading something years ago about somebody who cured it by bunging chewing gum in th’ole and then wondered why his clutch started slipping…

Had a crank seal go big time while visiting Ireland, my bro in law rigged up a 6mm copper pipe to drain the bell housing, this was rigged to run outboard, cable tied under the footrest to clear the tyre/brake. 6 litres of oil to get home and much of it ended up on my mate, Mr Scarborough, who ran behind in case I broke down, Thanks Mate!G.