primary lubrication

[RDfella]

Members will be used to my ranting on about the evils of oil in a primary case - but here's a genuine question.
As referenced above, I usually run my primaries dry, but now that I have an electric starter fitted, the gears in the primary need a little lube.  My clutch worked perfectly (6 spring S/A type) before I added oil (ATF). After that, clutch slip made the bike un-rideable; more that 1/4 throttle in first / second would promote instant revs and 4th was no-go.  So clearly ATF is not suitable. But what is? I'm thinking something thick enough not to soak onto the plates, like EP 90 or 140 (the latter used in Villiers primaries). Suggestions?

PS: I've just added 2 more clutch plates in search of extra friction, but not tried it yet. Primary is currently dry.

[Black Sheep]

I use tractor universal 10-30. Although it's primarily a diesel engine oil, it's also suitable for hydraulics (I use it in the forks too) and, importantly, it's also recommended for oil-immersed brakes, i.e. no anti-friction additives. Therefor ideal for clutches that get oily. And it's freely available and cheap.   

[Triton Thrasher]

Cork works better in an oily situation than most other friction lining materials.

I found that made more difference than type of oil.

An extra two plates (four lined surfaces) must make a difference though.

[muskrat]

G'day RD.
(6 spring S/A type) There's your problem LOL.
I use ATF in the plunger. The only time it slipped is when engine oil got into the primary (bad wet sump motor with no crank seal).
Whichever oil used it must not contain friction modifiers.
Castrol 4T motorcycle oil would be my 2nd choice.
Cheers

[rustydusty]

I recently re-acquired my ‘60 A10 after trading it to a friend who completely rebuilt the entire drivetrain but never started it. I noticed that he filled the oil tank and transmission, but never put oil in the primary side. Am I correct in using ATF?

[Worty]

I recently re-acquired my ‘60 A10 after trading it to a friend who completely rebuilt the entire drivetrain but never started it. I noticed that he filled the oil tank and transmission, but never put oil in the primary side. Am I correct in using ATF?

ATF is fine.  I use 4T oil in mine as I have 20l of the stuff for the Kawasaki.

[muskrat]

G'day Rusty.
As I said above. The primary only takes a cup full so the clutch isn't soaked in it. The only oil you can't put in is modern friction modified car/truck oil. If it has a picture of a motorcycle on the bottle it's safe.
Cheers

[Worty]

G'day Rusty.
As I said above. The primary only takes a cup full so the clutch isn't soaked in it. The only oil you can't put in is modern friction modified car/truck oil. If it has a picture of a motorcycle on the bottle it's safe.
Cheers

Which are friction modified Musky?  I used to have 20/50 and (for a time) a semi-synth 10/40 in mine with no clutch slip.  Now I use the Kwaka 4T bike oil.  I also tend to top it up to the level of the tube (so it runs out the bottom) - is that more than a cupful?

[muskrat]

G'day Worty.
Here we go another oil topic LOL.
Just about any CAR/TRUCK engine oil made in the last 30 years is friction modified. Full/semi synthetic oil is friction modified unless it states for motorcycles with wet clutches. Your Kumansukme 4T oil is good.
Book says 225cc = 225ml, one cup = 250ml.
Cheers

[Worty]

G'day Worty.
Here we go another oil topic LOL.
Just about any CAR/TRUCK engine oil made in the last 30 years is friction modified. Full/semi synthetic oil is friction modified unless it states for motorcycles with wet clutches. Your Kumansukme 4T oil is good.
Book says 225cc = 225ml, one cup = 250ml.
Cheers

Heh, cheers Musky!  Must have got away with it a bit there then! Blissful ignorance, although I did give thought to the fact that in the 'old days' it was 20/50 everywhere, whereas now it has all the additives.  Not so simple as chucking the 20/50 in thinking it's the same as the old Castrol.  Still, you live and learn!