slipping clutch

[Greybeard]

Where can I get me one of them special tools?

Looks like you have a very early petrol tank with speedo in the tank.

[Viking]

I have been “playing with” BSA & Triumph bikes from the 50ties since the 90ties
In general, the 4 spring clutch, is working well, (If all components is in good working order).

Slipping is generally caused by either weak springs or oil contaminated friction plates.

They can either be contaminated by using engine oil in primary cover, or seeping engine oil from the crank shaft housing, if the engine suffer from “wet sumping”.
To cure the problem:
A)   Replace the clutch plates with new high quality frictions plates. Or

B)   Wash the old plates in pure petrol, to wash off residue of oil.

(For a quick and dirty ( with fire hazard and great danger !! ) solution: pout ½ liter of pure petrol in to the primary cover, run the engine for 5 minutes with the clutch engaged. This wash off oil on the plates, and drain off the petrol, the add the proper amount of ATM oil)
BUT this quick and dirty. Requires a standby fire fighter canister !

Do not use engine oil in the primary cover, it contaminates the clutch friction plates and gives a slippery clutch.
I use ATM F type oil. Like CASTROL DEX II   mineral based automatic transmission oil.

[Greybeard]

Do not use engine oil in the primary cover, it contaminates the clutch friction plates and gives a slippery clutch.
I use ATM F type oil. Like CASTROL DEX II   mineral based automatic transmission oil.

I took that advice for my machine.

[oldbeezageezer]

I have just fitted a SRM complete clutch and say DO NOT use TQF, ATF or fork oil as they have antifriction additives which will cause clutch slip. Only engine oil 10/30 or 10/40. So I am going with their recommendations.

Haven't road tested it yet as still got to sort out correct footrest parts cos mine have duff splines.  Ran the bike on the bench and before fitting chaincase and the clutch operates well.

Alan

[Triton Thrasher]

SRM say some strange things.

[a101960]

I have just fitted a SRM complete clutch and say DO NOT use TQF, ATF or fork oil as they have antifriction additives which will cause clutch slip.

Utter nonsense! I have used ATF in my primary chain case for over 14 years and my clutch has never slipped. What are SRM talking about? These are the same people that say they will not honour the warranty on a rebuilt engine if you fit an external in line oil filter. An automatic gearbox is full of clutches that is how they work. Same as they say use only mono grade oil. By the 1970s BSA recommended using multi grade oil in both the engine and gearbox.
John

[Johnny J]

"Do not use engine oil in the primary cover, it contaminates the clutch friction plates and gives a slippery clutch.
I use ATM F type oil. Like CASTROL DEX II   mineral based automatic transmission oil."


Sorry, but I believe BSAs own Instruction Manual before anything else, running engine oil without any problems what so ever...
Don't think every BSA owner since like the 40's has been driving around with a slippery clutch.

[muskrat]

I agree with John & TT. The worst thing to put in the primary is modern multi grade car engine oil. They have friction modifiers that will kill a clutch in no time flat. If I use oil it's a motorcycle oil for wet clutches (Castrol 4T)
Car automatics have a clutch pack just like your bike but one for each gear.
Cheers

[muskrat]

Johnny got in ahead of me.
Johnny, engine oil didn't have friction modifiers back then.
Cheers

[RichardL]

I'm no expert in this, at all. When I first rebuilt my bike and fired it up in 2006 (and knew even less), I had 20W/50 in the primary case, slightly modifying what Haynes was suggesting. The clutch worked, as far as I knew, fine. Then I changed to ATF, based on advice in the forum (I had yet to reach "Dazed and Confused" status back then.) I did notice the improvement. I'm too lazy to do A/B testing on it to relive the differences now that I've ridden an A10 some thousands of miles (in a circle around my house). What I would argue to those who may know better is that the oil or ATF that is being flung wildly around inside the chaincase somehow stays off of the clutch by centrifugal force or otherwise. I would be very surprised if the inside of the chaincase is not a dense blend of mist, droplets and streams of lubricant leading to "wet" clutch. 

Richard L.

 

[duTch]

 
 

Where can I get me one of them special tools?

   Trade secret-"pat. pending"

 Richard-that maybe moderately true about misting, probably best way to find out is remove the inspection cover while still running after a ride and have a bopeep. I suspect most oil would be flung linear to the chain. .. And only until the chain has flung enough that the level drops to bottom of chain level. ..
 Re: ATF- I don't want to turn this into an oil thread .. But only recently did I realize there are several different types of ATF- But which one best for P.chain and forks(recommended for both my bikes)..

[Rocket Racer]

Wouldn't it be more accurate to say that our clutches "basically run wet in a controlled amount of oil"? I can't believe that running anything like dry was planned in the original design. I'm guessing that they ditched the early dome when they realized that didn't keep out the oil anyway, and the clutch still worked fine (for the era). Here is a place where my own limited experience with other motorcycle clutches comes in and leaves me wanting.  It seems to me that the wetness in our clutches provides a degree of smoothness in our takeoffs and downshifts.

Richard L.

Can't really agree with that; the primaries run beautifully dry...however the chain hates it and quickly becomes noisy. I ran dry primaries on a number of race engines and the only issues were chain related.
The oil is really only there to lube the chain and sprockets. However (again) the oil can contaminate the plates, typically where an engine has sat and cause slip and/or drag to an otherwise vaguely useful  clutch. A heavy oil  won't throw clear well, something I believe the lighter ATF does better.
On my race A10 I'm running a ventilated dry belt BNR clutch, no oil goes anywhere near the primary.

For a slipping clutch I would typically strip , clean and inspect so I at least knew how poked it was. I'd also probably refit it while I pondered how long I had to save up for a decent clutch.
I ran a 6 spring in my B33 for over 25 years quite happily and parts are readily available at least.
Sadly the 6 spring clutch was probably most suitable for a washing machine rather than a motorcycle. Not one of BSA's finest designs, but it can be kept serviceable.

[Johnny J]

Johnny, engine oil didn't have friction modifiers back then.
Cheers

Don't think there are any in the single grade Classic oil I use either...

[duTch]

Off topic, but;
 

Looks like you have a very early petrol tank with speedo in the tank.

I had no idea what it was off, but finally figured a while back that it's from a first model '46 A7 'Vertical Twin'- but recent discussion told me first A7 was '47, so now I just don't know 

[Rocket Racer]

Off topic, but;
 

Looks like you have a very early petrol tank with speedo in the tank.

I had no idea what it was off, but finally figured a while back that it's from a first model '46 A7 'Vertical Twin'- but recent discussion told me first A7 was '47, so now I just don't know 

Just shots in the dark, but both the XB31 and ZC11 had tank top speedo's.