ET: Engine (Twin) Oil Leak

stumpy lord

Well Known and Active Forum User
Non-VOC Member
If the oil leaking out is similar to the colour of the oil in the gearbox, it could likely be the output shaft bushes have collapsed, thus the red/gold tinge coloring of the oil........not an uncommon problem, and not too difficult to repair, if not messy.
If as you say, the gear box oil is contaminated the( oil should be clear ) I would consider draining the oil and refilling with a good E P oil. In all the years I have owned a vincent I have never seen the oil come out contaminated as you described , possibly the machine has been sitting for a long time and, condensation has formed in the gear box causing some corrosion to form.
Whilst doing that you could always calibrate the the dip stick.

An old simple dodge to prevent oil seeping down the main shaft is tap the bush G16 (should that be G17? BigEd ) back into the shaft G4 and fit a very fine O ring between the end of the shaft, and G26 ratchet spring cup.
 
Last edited by a moderator:

Bill Thomas

Well Known and Active Forum User
VOC Member
How are you checking the gearbox level ?,
Leaning on the wall ? or the back stand ?.
Always wipe the stick every time, I got caught out years ago,
The splash can stay on the stick a long time !!.
I also use thick oil in the Gear box, 80 or 90, That also might help ?.
 

nigsey

Well Known and Active Forum User
VOC Member
Many thanks for all your replies and suggestions. The latest news is that I drained the gearbox and refilled with Castrol EP90, hopefully that oil is acceptable in a twin. The drained oil was reddish brown in colour with minute glittering particles in it, at the bottom of the container there were a small amount of grey sludgy bits that looked more like aluminium. I fired the motor up and went for a short ride and no oil whatsoever came out from underneath. I checked the oil level in the primary case and it looked low but looking through the inspection cap the colour of the oil deposits on the sprockets appeared to be the same reddish brown, so I’m wondering if the problem does come from this side.
 

nigsey

Well Known and Active Forum User
VOC Member
How are you checking the gearbox level ?,
Leaning on the wall ? or the back stand ?.
Always wipe the stick every time, I got caught out years ago,
The splash can stay on the stick a long time !!.
I also use thick oil in the Gear box, 80 or 90, That also might help ?.
Thanks Bill, the bike is up on the Hills centre stand.
 

Bill Thomas

Well Known and Active Forum User
VOC Member
Vincents are funny old Bikes, As an old racer I like big breathers,
As Peter said pressure can go from one place to another,
But not all bikes suffer from this.
The gearbox breathes from the flats on the dipstick, Then through small holes in the filler cap,
The chaincase should breath through the gap between the dynamo or alternator and the case,
BUT some of us seal it there to stop oil leaking, Which could make pressure in there ?.
But as I said One bike may do it and another not !.
Guess which way I have gone !!.
 

Attachments

  • first ride 2020 lightning.jpg
    first ride 2020 lightning.jpg
    679.3 KB · Views: 31

Cyborg

Well Known and Active Forum User
VOC Member
Reddish brown sounds a bit like rust contamination, not totally unheard of in the primary chain case due to condensation. There is a long explanation of this phenomenon on this forum somewhere, I would search Hugo Myatt, basically the engine can pressurise the chain case through the main bearing, and the pressure in the chain case forces oil into the gearbox, I am not for one minute saying this a definitive explanation of your problem, but perhaps something you should consider, if that does prove to be the problem, I have to tell you there is no quick fix.
F19B8421-D0E9-4696-A4DC-C8CC6E1B5D53.jpeg
 

timetraveller

Well Known and Active Forum User
VOC Member
I really do not want to be depressing about this but if the gearbox oil had bits of any colour metal in it then something is, or has, broken up. It sounds as though one or more of the Oilite bushes has collapsed, to give the red/bronze colour, and the aluminium sludge sound like something is wandering about and chewing up the casting somewhere. It is not a big job to remove the primary chain case cover, the clutch and then the access hole to the gearbox. Having a look might save you a lot of money.
 
Top