The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: TaylorP on 15.03. 2021 21:43

Title: Clutch Slipping when kicking Over
Post by: TaylorP on 15.03. 2021 21:43
I'm having some issues with the clutch slipping on my Super Rocket when I'm kicking it over. I've drained the oil and removed the chain case cover and the problem has disappeared. I'm using Silkolene classic straight 40 and wonder if I should switch to ATF. Has anyone had similar issues?
Title: Re: Clutch Slipping when kicking Over
Post by: Triton Thrasher on 15.03. 2021 21:48
SAE40 is awfully thick for a primary drive.  Is it recommended somewhere?
Title: Re: Clutch Slipping when kicking Over
Post by: TaylorP on 15.03. 2021 21:56
It was recommended on the Facebook BSA site to use engine oil.
Title: Re: Clutch Slipping when kicking Over
Post by: a10gf on 15.03. 2021 22:27
Should'nt it work fine in "any" oil? Was originally made for same as goes in the engine.
Questions would be plates & springs in good shape \ correctly adjusted tension \ correct freeplay.

ps, an intro post is always appreciated :O)
Title: Re: Clutch Slipping when kicking Over
Post by: berger on 15.03. 2021 23:41
don't oil the plates it's a dry clutch with oil for the chain
Title: Re: Clutch Slipping when kicking Over
Post by: ellis on 16.03. 2021 03:20
Hi TaylorP,

I had similar problems using SAE 40 oil. I changed to SAE 20 and the problem went away. You could also try lowering the oil capacity a little as the oil is mainly there to lubricate the chain and the clutch basket bearing, although it only relies on a bit of fling now and then. Hope this helps.

ELLIS
Title: Re: Clutch Slipping when kicking Over
Post by: Black Sheep on 16.03. 2021 06:43
I use 10w-30 tractor universal oil. It's a diesel oil but also used in hydraulics and oil-immersed brakes - no anti-friction additives. Perfect for primary chaincases and forks for that matter. Added bonus - it's cheap and easily available on-line.
No clutch slipping in the A10 or even the Norton Atlas.
Title: Re: Clutch Slipping when kicking Over
Post by: Colsbeeza on 16.03. 2021 06:48
For Interest.
I have had a slightly different issue with my new 4-spring clutch. On assembly, I installed the 20 rollers using some grease to hold them in place. I had 30 Monograde oil for chain lubrication. The operation was great! but after a few hours the clutch would not disengage, making gear changes into and out of first gear impossible. I think in hindsight, I used lithium grease as that is what I had on hand.
On dismantling, there was black gunk on the steel plates which would only come off with my 8" rotary steel brush attached to my grinder. The gunk was so stubborn, I thought I might have to resort to a file. The clutch came from Draganfly as a special ( interpret as bargain) offer. I cannot see anything wrong with the fibre plates, so assume the lithium grease residue was to blame.
I am refitting it tomorrow, and will lay the clutch centre on its back and install the chainwheel horizontally ( I did that last time OK but with grease) and use a little light Automatic Transmission Fluid DX-111 on the rollers. Then fit the inner basket and place the whole thing on the gear mainshaft. Will use ATF DX-111 for chain lubrication, it is about the same viscosity as SAE 20, which I cannot seem to find here in Australia. If the problem returns, I will toss the fibre plates and get a set of Surflex plates.
Has any member had such a problem?.
Col
Title: Re: Clutch Slipping when kicking Over
Post by: TaylorP on 16.03. 2021 07:43
I suspect the oil level has been too high, I'm not yet sure how, but it could be  that I hadn't let sufficient oil out of the level plug. It could also be wet sumping but I don't think so. The question is now, do I need to strip and clean the plates, given that its working OK without oil. Also do I refill with a different oil ( any recommendations?) Thanks again for the help. I will write an introductory post later today, as usual just came in from the garage with lots of questions.
Title: Re: Clutch Slipping when kicking Over
Post by: berger on 16.03. 2021 09:50
yes clean the plates and do some research on the level plug, people have been known to change them over the years, I had one that was in a bsa case that was 3mm taller than my old one and that's a lot of oil
Title: Re: Clutch Slipping when kicking Over
Post by: ellis on 16.03. 2021 19:12
I would limit the oil capacity in the chain case 190cc max. I never had a clutch problem and this amount of oil was enough to lubricate the chain.

ELLIS
Title: Re: Clutch Slipping when kicking Over
Post by: muskrat on 16.03. 2021 19:15
G'day TaylorP.
I have used bearing grease to hold the rollers without any issues in the past. ATF is my preferred lubricant (easy to spot a leak as it's red). Friction modified oil is a no no.
Wet sumping into the primary is usually only on early (pre 53) plungers and rigids. Your SR will/should have a crankshaft seal.
Cheers
Title: Re: Clutch Slipping when kicking Over
Post by: TaylorP on 16.03. 2021 20:47
OK quick update, contrary to what I found last night the clutch slips without the chain case cover on. So its a slightly different problem. Heres what I've found so far.
- clutch adjustment at the basket, way out, must have been slipping like this for ages.
- clutch friction plates appear to be new, pressure plates nearly new, probably how the previous owner got away with the above.
-Clutch plates have lots of oil on them, this could be me over filling or the previous owner, I will never know.
- after initial tightening down of the clutch springs and seeing a good improvement, I've stripped and cleaned the clutch and I'm in the process of reassembling it and deciding if I go for ATF or a lighter mono grade (best I can find so far is a straight 30) thanks for the help i will keep you posted.
Title: Re: Clutch Slipping when kicking Over
Post by: RDfella on 16.03. 2021 21:27
Many modern cars use oils as low as 10 or even 5. Admittedly multigrade, but should be widely available. I learnt a long time ago that oil and clutch plates don't mix (the ones like ours, not modern bikes).
Title: Re: Clutch Slipping when kicking Over
Post by: Sav on 18.03. 2021 09:11
Had problems with my A10SR clutch slipping with fairly new surflex plates and researched it quite a bit

I use JASO MA oil  (no friction modifiers) in the form of Shell Advance 10-40 which is specifically made for wet motorcycle clutches.

I have not had a problem since.
Title: Re: Clutch Slipping when kicking Over
Post by: Slymo on 06.05. 2021 01:24
It should be fine with oil on the plates, most of it is centrifuged off when in use but it is a wet clutch by design. I use ATF but ordinary engine oil shouldn't make it slip unless you've got molybdenum disulfide or similar in it.  If its a 6 spring original check that the pressure plate fits on without interference to the basket as even a slightly restricted fit will mess with the operation. You may have to bend the tabs on the basket that penetrate the pressure plate so that it fits on nicely. then spend a lot of time adjusting it so that it lifts evenly. Someone said that they used a DTI but I've found that careful eyeing up will give a good result. The difference between a clutch that slips and one that doesn't is very subtle and overtightening makes for an unpleasant riding experience and puts a lot of strain on the 1/4" posts that will pull out after time if you are brutal. I remade all of mine and riveted them in when one popped out. A lot of shagging around but a completely usable and pleasant clutch to use I've found now its right. If you've got a four spring replacement just forget everything I've said :)   
Title: Re: Clutch Slipping when kicking Over
Post by: Billybream on 06.05. 2021 04:22
It's worth spending time getting the clutch pressure plate to lift evenly, setting with a dial indicator or some form of pointer is highly recommended, even lift within a few thousands  of an inch will vastly improve clutch operation.
The standard pressure plate can be changed for a machined alloy version with top hat type bearing, this modification is highly recommended.
Your 4 spring clutch is very good and once set up correctly should result in 2 finger operation and give reliable performance.
Title: Re: Clutch Slipping when kicking Over
Post by: Swarfcut on 06.05. 2021 09:49
 Just read this thread from the beginning. I reckon Col's problem of deposits on the plain plates is more down to the poor quality of the friction material or bonding adhesive. For material to be leached off by lubricant in such a short time is not how these plates usually behave. A non bargain if ever there was one.

 For those folks having similar problems with the earlier S/A 6  Spring clutch and its penny pinching design, I've noticed this contraption also comes comes in various guises adapted to fit the models in the contemporary B, M  and early C range. For example there are varying depths of clutch basket, flat and dished pressure plates, corresponding different numbers and combinations of plates and clutch centres with different styles of driven tabs. Plain Clutch Plates also vary in thickness, some pattern types are extremely thin. Add to this the wear that takes place, notching components that should slide and there you have a recipe for a clutch that sticks or slips.

 If you have a problem with this clutch it is worth checking that the basic parts are correct and not an assortment of bits from different models. Lower powered models from the other ranges have less plates for starters. A previous owner may have fitted whatever was to hand, and if the bike came as a basket case, nothing can be considered to be the right parts, and yes, ebay sellers haven't a clue either so be careful. That Rocket Pressure Plate  could have started life on an M20 or C11....certainly not the right part.

 Set up correctly the 6 spring pressed steel centred clutch is fine, but why BSA moved from the superior Plunger type 6 spring robust centre design can only be down to the cost accountants. The later 4 spring design cribbed from Triumph addresses most of the failings, going back to a solid or cush type centre but as here can still be problematic for the simplest of reasons. Use the "oil flicking past the hole" fill method to run the primary chain in oil without overfill allowing a high level of oil to enter the clutch.

 Swarfy.
Title: Re: Clutch Slipping when kicking Over
Post by: Colsbeeza on 06.05. 2021 11:20
Thanks Swarfy,
I have cleaned the plates, (which came from D'Fly) and will use 190mls of ATF. If the problem persists, the plates will be turfed and new ones from SRM or whoever.
Col
Title: Re: Clutch Slipping when kicking Over
Post by: KiwiGF on 06.05. 2021 12:07
Thanks Swarfy,
I have cleaned the plates, (which came from D'Fly) and will use 190mls of ATF. If the problem persists, the plates will be turfed and new ones from SRM or whoever.
Col

The friction modifiers in car engine oil DO mess up set clutches and makes them slip (it even happened on my suzuki 1400 when I skimped and put car oil in it instead of motorbike oil) but in that instance just swapping the oil to the correct type made the slipping go away.

I agree with the earlier post that the 6 spring s/a clutch is pretty good if you have all the correct parts and set it up with a dial gauge.

I reckon having incorrect spec clutch parts from other models (pre unit singles etc) is partly responsible for the bad reputation of the 6 spring.

I fitted a Newby belt drive and clutch to my A10, and found the Newby clutch is only slightly better in operation than a 6 spring, but I fitted the Newby kit for others reasons.
Title: Re: Clutch Slipping when kicking Over
Post by: berger on 06.05. 2021 14:22
i must say a lot of 6 spring trouble comes with pattern part middles that flex, break or just disintegrate like mine did. when i found and fitted an original BSA one with the reinforced bits and made of toughened steel you can have a very good clutch but a lot of people prefer the 4 spring triumph one. i even swapped mine when i found a triumph one