The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: Rgs-Bill on 02.01. 2014 22:48

Title: Proper oil weight//Primary case
Post by: Rgs-Bill on 02.01. 2014 22:48
BILL here, I would like to get a consensus from several of you fellas, on what is the best weight and type of oil to run in a primary chain case..  Now the guy I bought it from (40 years ago) said it had a Barnett dry race clutch in it. (I have not ridden it that far maybe 5K)  Well does dry mean I should not run any lubricant in the case or just reduced down from the 8 ounces the Haynes calls for.  I get a bit of cachunk when shifting from neutral to 1st gear, however much less if I give it 3 seconds after pulling in the clutch lever.  Now I get a bit of thunk going from low to second, then nothing going to 3rd and 4th,  down shifting is exactly the same.  I did the old  "Good Eye"   with the primary case cover off, and had to adjust for level lift off and landing, now I do not have any stop light creeping, like I used to have, but me thinks the mono weight 40 Bradd Penn oil in the chain case, might be too thick, sticking the drive plates some ??? not sure.  You have to have something in there for the clutch basket bearings and to cool the primary chain down right ????

     waiting for all of the comments
     bike is now winterized until March
Title: Re: Proper oil weight//Primary case
Post by: muskrat on 03.01. 2014 13:15
G'day Bill. The oil in the primary is mainly for chain lube, the center bearing relies on splash and mist.
 ATF is an oil designed for wet clutches (in an auto car box there is one clutch pack for each gear) and so will not harm and cause slippage in our clutches. Engine oil designed for modern wet clutch motorcycles like Castrol Active 4T 15/40 is my 2nd choice. A 30, 40 or 50 grade mono would be OK. Most modern car oils contain friction modifiers that will cause slippage (the primary is the only place I don't use nulon) and if wet and unused for a period of time will gum the plates together.
 The clutch plates can run dry but they do get a bit of oil which is flung off. I'd say most mass produced motorcycles for road use have a lot more oil in the primary than really needed, sort of a safety factor. Important for any primary with a slipper chain adjuster like our rigid/plungers and A65's.
 On my racer I had a chain driven 4 spring clutch in an open dry primary. The bearing would get a fresh gob of grease before each meeting and the chain would get a spray of chain lube before each race. New chain and rollers every 2 or 3 meetings. 1st prize in one race was a roll of reynolds chain, it lasted a few years. The only way to run a dry clutch on the road is with a belt and a sealed bearing. I haven't had to look at the cafe's for a few years now.
 Your slow gear changes are probably more to do with the oil in the box. I'm not overly fussy with what I put in there. Some times they get 80/90 gearbox oil other times if I'm out it's 20/50 engine oil but always with my favorite additive *whistle*. In years or racing I never had to look inside the standard A7SS box, the only time I used the clutch was at the start line. Changes were as quick as any oriental bike 30 years younger.