Misc: Everything Else Comet: primary chain oil leaking out mainshaft hole behind clutch

Bradley Burt

Well Known and Active Forum User
Non-VOC Member
I'm sure this has been discussed plenty of times before, but how do you seal off the hole in the inner primary cover that the gearbox mainshaft goes through to prevent primary chain oil leaking out?
 

Dave Hulstone

Well Known and Active Forum User
VOC Member
Send it to Greg Brillus on the Gold Coast? He’s the only bloke I know who can successfully stop these bikes from leaking oil. And he’s here, in Australia!
 

b'knighted

Well Known and Active Forum User
VOC Member
Remove the level screw in the cover to drain the oil to the correct level.viewing the oil through the filler cap should let you see that the bottom of the lower run of chain is touching the oil enough to lubricate the chain. The visible oil should be fairly clean, very similar to the condition of the oil you put in.
If it is conterminated with engine oil it is probably a result of the engine dumping while parked, then crankcase pressure pumping this oil through the main bearings.
 

Bradley Burt

Well Known and Active Forum User
Non-VOC Member
I'll try to better explain my question.

The hole in the inner primary cover that the gearbox mainshaft goes through is oval shaped to allow the gearbox to be adjusted forward and back. So the mainshaft isn't an oil tight fit through this hole. Is there a way to seal this hole so there's no oil flying out when the bikes running?
 

Dave Hulstone

Well Known and Active Forum User
VOC Member
I guess what we are trying to say is this is a known problem area with the Comet set up regarding oil leaks. As you know, the adjustment slot cannot be sealed up to stop splashed up oil escaping via the main shaft, or it ceases to be an adjustment slot. There are some experienced Vincent fettlers like Greg Brillus or Ken Phelps for instance, out there who successfully manage to cure this by fashioning some sort of disc that fits perfectly around the shaft but isn’t fixed, allowing adjustments to still take place. These can be made from a flattened coke can amoungst other things. Ken did a write up on this once in MPH.
I think the other guys are referring to keeping the oil level spot on so making sure no oil is coming in from the engine and also making sure the primary chain case isn’t becoming pressurised? Mine is in with Mr Brillus as we speak getting sorted, which he has successfully done before but I’ve since had an Alton electric starter kit fitted by a non Vincent wise mechanic and it now chucks oil out constantly, or it did until I drained it completely in frustration and took to oiling my chain with chain lube through the filler hole. Not ideal I know, and I risked overheating my Conway (Honda) clutch.
I hope some of this helps.
 

Bill Thomas

Well Known and Active Forum User
VOC Member
The bottom end has been together since 1977,
Used for road and raced when the twins went bang !!,
Standard gearbox and clutch,
Super little Bike, Just wish they were little faster,
Can't see why they were not made as 600 cc, Like a Panther ?.
 

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