The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: KeithS on 07.05. 2013 20:31

Title: Stiff clutch
Post by: KeithS on 07.05. 2013 20:31
I'm new here. Just got myself 1962 A10 and want to get it to the MOT test but the clutch is really stiff.
I've oiled the cable which seems fine. The pushrod moves freely when feeling from the gearbox side. Attached is a photo of the clutch which I haven't et stripped and the springs appear to be under the least possible tension.
The only thing which is rubbish is the slop in the lever bush at the top of the gearbox.
Any ideas? 
Title: Re: Stiff clutch
Post by: chicago on 07.05. 2013 20:37
Hi there fella, not sure of the setup on a10s but I don't think the nuts are the right ones, mine has six brass type nuts. Might be that having a nut plus a locknut might be taking up more room on the thread than a standard brass type nut, thus putting more tension on the spring ?. I could be wrong but I'm sure someone on here will be able to point you in the right direction if I am wrong. All the best fella, chicago.
P.s welcome to the forum and the world of bsa.
Title: Re: Stiff clutch
Post by: KiwiGF on 08.05. 2013 07:58
Ive got the same clutch with locknuts like yours and i have 2 threads showing which would indicate i have more compression on the springs than you have, but anything less and my clutch slips. I think single lock adjustment  nuts were fitted to later models.

Your pressure plate looks like the earlier type as later types have a stronger basket and the slots in the plate are larger as a consequence.

I think you will need to strip the clutch and check you have the right number of plates, not an extra one to compensate for wear, and that there are no notches in the basket and clutch wheel etc. Either of which might cause stiffness.

I suggest you use a dial guage to ensure the pressure plate lifts off evenly when you put it back together.

In my experience the 6 spring clutch is a bit harder to operate than others, like the triumph clutch fitted to later models.

Youve checked the adjuster in the gearbox, the one pushing on the rod that end? And the ball is in place in that adjuster?
Title: Re: Stiff clutch
Post by: Topdad on 08.05. 2013 15:08
Hi and welcome, hope you enjoy your bsa. You have the six spring clutch the alternative mentioned by Kiwigf if the 4 spring triumph/bsa fitted from roughly ,I think '59 prob wrong but certainly the later models . Yours is I'm afraid my pet hate due I think to the fact it takes more time to set up which it needs to work properly . However don't forget the simply part ,you say the cable is lubed but how is the run ,any kinks or places where it's obviously tight , pos  the rear plate cover where it goes through a hole to get to the top of the gearbox, worth checking then follow the advice of the guys who have these units. If problems persist put a 4 springer on your shopping list and get when poss. Just my personal feelings and I'm sure one of the guys who know these will help, regards and best of luck BobH.
Title: Re: Stiff clutch
Post by: bikerbob on 08.05. 2013 19:15
I had a similar problem a very stiff clutch I lubricated the cable adjusted the clutch correctly and still it was stiff to operate the problem was caused by the nipple at the lever end binding in the lever a couple of drops of oil and hey presto everything works smoothly lesson learned was don't go for the complicated solutions first.
Title: Re: Stiff clutch
Post by: KeithS on 08.05. 2013 19:37
Thanks for all your replies.
Cable is nice and free.
Cable run is OK.
Clutch now dismantled and has five of the inner ball bearings missing (but I can't see how that would affect the stiffness of operation).
Also the clutch backplate is out of alignment and has at some time caused the chain to gouge a groove in the rear of the chaincase inner so I will have to try moving the gearbox to bring it back into alignment.
Can anybody say how much cork should be standing proud of the chainwheel at the back (gearbox side) - I seem to have very little.
Title: Re: Stiff clutch
Post by: chaterlea25 on 08.05. 2013 22:36
HI Keith,
 the primary case may be pulled outwards towards the frame at the mounting just underneath the photo bottom.
Spacer/ washers should be added here so as not to distort casing

Heavy clutch operation can be caused also by having the clutch pushrod / actuating lever inside the outer cover
not working at the correct angle,same goes for the cable /operating lever on top of the gearbox
Your worn casing maybe part cause and symptom,
There were /are also different length spring cups fitted to different models which use fewer clutch plates
was there much tension when you undid the nuts?
The chainwheel inserts are fairly worn

Title: Re: Stiff clutch
Post by: KeithS on 08.05. 2013 22:43
Thanks John
Does that mean a new chainwheel or can inserts be inserted?
I'm even more disappointed now that i find the 6 spring clutch was supposed to have not been used on a 62 bike!
Not too much pressure when I undid the screws.
There is a lot of slop in the operating lever on top of gearbox - the bush must be fairly worn.
Title: Re: Stiff clutch
Post by: chaterlea25 on 08.05. 2013 23:09
HI Keith,
I am not sure if inserts are available, or how thick they were originally
I am not a fan of the six spring clutch *roll* *roll*
I suppose most of the ones I have dealt with were well worn, I normally replace them wiuth the 4 spring unit
That said there are crap 4 spring clutches out there too!!!!
Some of the replacement  4 spring chainwheels are very thin on the outer where the plate tongues fit leading to the plates chewing up the slots and causung more problems *sad2* *sad2*
The lever runs straight in the alloy gearbox case  *ex* I have repaired them by boring and fitting bushes to the case

Title: Re: Stiff clutch
Post by: KiwiGF on 09.05. 2013 05:52
Hi Keith, the inserts are not much thicker than the wheel from memory, basically they have some life left if there is no metal to metal contact!

I think they are referred to as "Ferodo" inserts and I have not found any available, but I suspect this is not the source of your problem anyway. Cork cut to shape DIY style could probably be used in place of the OEM "Ferodo" material I guess.

My guess is that there is too much pressure from the springs and I suggest you do some road testing to see how much you can back off the springs before the clutch slips.

You can do this with the primary cover off the bike, so it's not too tedious, in fact this is a good idea anyway before you fit the cover and add oil - to see if you have got the springs right and no excessive drag etc.

You may have to run with only one nut on the springs but that should be ok for  short run, you could loctite them if it worries you.

If you can establish the clutch does not slip with the adjusters backed off then you can start looking at "why" - and maybe get new springs/cups etc.
Title: Re: Stiff clutch
Post by: A10Boy on 09.05. 2013 09:03
Firstly you should find inserts available in UK [I'm guessing you are in UK as you mention MOT] try C+D Autos or Vale Onslow. Secondly, I'm not sure of your budget but in my opinion swapping to a 4 spring clutch is much preferable than spending money on the older 6 spring effort. You will need the adaptor which is readily available and costs around £50 and the clutch itself is often sold as a kit for around £300. Not insignificant I know, but well worth it if you can.
I have a 4 springer on my A10, I fitted an alloy pressure plate and springs [SRM] that has a thrust bearing which helps lift the plate squarely so set up is a doddle, the level action is no heavier than a japanese bike's. You should be able to get close to that with a new one.



Title: Re: Stiff clutch
Post by: BSA_54A10 on 09.05. 2013 11:38
The M , B & C series all used 6 spring clutchs but they had less plates so used a shorter spring & spring cup.
C series parts are a lot cheaper than A series parts so no doubt some cheap skate ahs bought the cheapest possibile ( wrong ) parts.
The gouges in the chaincase can be attributed to the lost balls.
The chain wheel flops about all over the place when you pull in the clutch with good bearings in, even worse with a bad one.
A lot of things go to making a heavy clutch.
If the actuating lever is at 90 deg to the cable ( or even a more accute angle ) before you start to pull on the cable it will be vry heaqvy as your are actually trying to stretch the cable not pull the lever.
As preciously mentioned the cable must be both free to move and to rotate or you end up with a heavy pull.
And do not over look the handlenar lever.
there are severy different lengths and some will make the pull very hard.
Using a plain bolt in the lever fulcrum in place of a shouyldered one will also add to the pull.
Bike Beesa