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ET: Engine (Twin) Oil Leak from Gearbox to Primary Drive

Rob H

Well Known and Active Website User
VOC Member
Been noticing a rise in oil in the primary drive and fall in gearbox. I am guessing a possible cause is failure of the oil seal in the G2 gearbox cover plate.

Are there any other possible causes I would need to check?

regs
Rob
 
Last edited by a moderator:

greg brillus

Well Known and Active Website User
VOC Member
Oil can seep though the bolts that hold the cover door on, and the dowel at the bottom can leak if it comes loose for whatever reason.
 

CollingsBob

Well Known and Active Website User
VOC Member
I had this happen..The oil pissed out the back of the bike all over Tony Cording‘s bike as he followed me..It could be the seal, but for me 2 of the bolts securing the G2 had backed out, one of them had been ground into paste by the primary chain. I hosed out the holes with brake cleaner, put new bolts in with the threads slathered with a non-setting gasket maker ( not silicone ) and carefully lock wired all the bolts together.
 

greg brillus

Well Known and Active Website User
VOC Member
Of course the door to case could be the main leak, but you would need to remove it and look carefully at the mating surfaces (I would do this regardless if you have the primary stripped apart). Whilst the cover is off you can inspect the dowel pin and make sure it is secure (it is unlikely to be this pin but I have seen them loose) clean up all the bolts and threads (1/4 whitworth threads) check also the bolts as they are often stretched from folk over tightening them, if this is the case, then replace them all. I install the cover with a bead of Threebond sealant and I also smear some on the bolt threads before I install them all. This tends to stop the bolts coming undone, wire locking is ok, but I don't bother normally except the upper one at 1:00 o'clock that is wired to the detent plunger cap in front of it. Do check the G 24 seal, these can be overlooked often and they are easily damaged if the slots in the bearing retaining ring are butchered. Because of these slots there is little sealing purchase for the seal, so use a small amount of sealant to help the new seal go in, and press it in with a flat plate or socket to keep it square. Finally make sure all the surfaces and case threads are thoroughly clean before assembly.........Good luck with it all.......... Greg.
 

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