I have recently replaced the crank seals and also the large O ring on the disk valve cover but engine oil still seems to be getting through into the cylinder. Bike smokes a fair bit as a result. Does anybody have any ideas of what else I can do to stop the engine oil getting through?

I have recently replaced the crank seals and also the large O ring on the disk valve cover but engine oil still seems to be getting through into the cylinder. Bike smokes a fair bit as a result. Does anybody have any ideas of what else I can do to stop the engine oil getting through?

I would be 100% sure that the gearbox oil is passing between the centre crankcases

as it is only sealed by sealant as thhese engines aren't fitted with a centre gasket.

If you split the engine to fix it make sure you use a good quality case sealant

like THREEBOND engine sealant.

Do not use silicone houshold sealnt.

Cheers

I would be 100% sure that the gearbox oil is passing between the centre crankcases

as it is only sealed by sealant as thhese engines aren't fitted with a centre gasket.

If you split the engine to fix it make sure you use a good quality case sealant

like THREEBOND engine sealant.

Do not use silicone houshold sealnt.

Cheers

Thanks for the advice, that's a job to be done over the next few weeks!

Cheers Chris

Hi, from this conversation it sounds like crankshaft seals can be replaced without splitting the cases?? And how necessary is to rep;lace the rotary valve o ring as I am currently ordering parts and haven't included that?

Any advice welcomed.

Hi, Yes I replaced both seals without splitting the engine. One seal sits in the disk valve cover and the other sits in the magneto plate that sits behind the flywheel. (the flywheel cover bolts to this plate) I replaced the O Ring in the disk valve cover just as a precaution even though the original looked ok. Obviously, I have been unlucky in my attempt to minimise the work as I now have to split the engine to replace the sealant. I originally thought that there was a gasket between the two sides of the engine.

Cheers Chris

Well with the help of Feetfun [thanks Dave] and some advice from Martin on locking the engine with a bolt thought the cases we replaced the clutch side oil seal - still leaking and burning oil - bugger - is it worth doing the rotary valve o ring? or could I be up for a spilt the cases job?

Well she's been dismantled recently and the induction valve cover o ring looked stuffed ie flat it also appeared to sucking air thru cases. Splitting the cases was worth while as kickstarter engagement dogs were chipped. Piston still standard and didn't need re bore - so new rings only.

gearbox and big end was fine [those main bearings are huge].

Looking fwd to having her back together.

Well 7 months and i got the engine back and spent the last 8 hours in the shed putting her back together. Started second kick and sounded so crisp and as i rode off for a while and she felt great.....THEN she started smoking like a chimney [ you could smell the gearbox oil] and running badly. Exactly how it was before it was before it was stripped down.

In summary it has a complete rebuild with new parts and had the cases remachined and three bonded.

Is there any components on the rotary disc side that can be reassembled incorrectly to allow gearbox oil through? Although I doubt this is the answer as like I said its doing what it did before the rebuild.

Check the rubber manifold between carb and the tube of the disc valve cover for cracks that allow the engine to suck in oil.

(This rubber part is sadly not available anymore !!!)

Thanks, that's the only thing that makes sense at the moment.

Check the rubber manifold between carb and the tube of the disc valve cover for cracks that allow the engine to suck in oil.

(This rubber part is sadly not available anymore !!!)

.......Not correct, I have a source of remanufactured carb/disc rubbers if anyone needs them.

Thanks, that's the only thing that makes sense at the moment.

........Check the crank seal against the primary drive gear. I did a rebuild for a TC member at Christmas, and it ran exactly as you describe. I reckon I had reinstalled the old crank seal by mistake. When you check the seal on the gear if theres no or very little resistance, thats where your problem is. If you didnt rebuild it....make sure that this seal is in the right way round, and they have installed the disc vale O ring.

Edited June 3, 201214 yr by MartinM

.......Not correct, I have a source of remanufactured carb/disc rubbers if anyone needs them.

...

Extremly good news, (Have tried to get one nearly everywhere also been told by forum members at Trialforum Germany that they are not available anymore, I should have asked you first). I need them badly, you will get an E-Mail!

Cool thanks Martin we have done the crank side seal once and then had the engine rebuilt with new seals. Is it possible for a leak in the manifold to really chew through some gear box oil in your opinion.

Yep intake manifold spilt on engine side replaced with my no. 2 bike and she's running sweet as a nut . . its just like X mas - be practising with the daughter tomorrow for sure.