Clutch Problem

[bikerbob]

I have a1956 A7 with the six spring clutch, It has a serious oil leak from the back of the primary case. I stripped it down thinking all I had to do was fit a new felt washer and sliding plate. On inspection I found that a previous owner had fitted 3 new surflex plates and 2 old very badly worn ones also the chainwheel inserts were badly worn. The rear plain plate behind the chainwheel has been wearing against the sliding plate to such an extent that it was worn the heads off the 4 rivets that hold the center part of the sliding plate also the clutch sleeve collar that has the reverse scroll was badly worn. I purchased new felt washer and sliding  plate plus new chainwheel and 2 new surflex plates new sleeve collar with reverse scroll and new bearings plus the inner ballrace ring. I have rebuilt it up  but on start up something is still catching but it goes away if you pull the clutch lever in also the oil is still leaking badly out of the rear of the chaincase,  where abouts should that collar with the reverse scroll be situated it seems to me that it is too far into the sliding plate when assembled you cannot see it, those tags on the clutch sleeve that but up against the rear plain plate behind the chainwheel are just clear of the sliding plate.  Any ideas to solve these problems please.

[wilko]

Sounds like your inner chaincase is sticking out too far.

[duTch]

  It's a long time since I had a swing arm, so a bit hazy on detail, but wonder of it's possible that the engine/engine/g-box plates are on the wrong sides of each other....?

[chaterlea25]

H Bob,
Your problems are not uncommon
The first thing to check is the bolt from frame to inner case at the lower rear of primary
There should be a "spacer between the frame and case, this normally consists of a number of washers depending on how much of a gap is there
If no spacer is fitted it pulls the inner primary outwards and the plate fouls the clutch centre
If the front of the case has either too many or too thick gaskets with  the spacing plate this affects the sliding plate/ scrolled centre  fit as well
When checking the inner case fit replace the front 5/16th chaincase screws with added spacers so the front of the casing is clamped firmly to the  crankcase
I have found that the replacement felt washers act like a "wick" and suck oil out of the primary cases????

I also check primary chain alignment  before fittin the inner chaincase

HTH
John

[bikerbob]

Thanks for the replies. At the front of the primary case there is a gasket either side of the large circular distance piece, now the parts list that I have which is for A7-10 for 1954 -57 does not list this distance piece only a jointing washer if I was to remove that distance piece then there is already evidence that the cush drive nut has been fouling the outer chaincase removal of that distance piece will make that worse. As regards the rear mounting bolt there was no washers or distance piece present when I dismantled it because the case was against the frame I will have to dismantle the entire primary side again and see if there is some way I can get the rear chaincase to move further back. As  regards the oil leak when started it up there was a loud scraping noise which diminished slightly after a few seconds and went away altogether if you pulled in the clutch lever but returned when the lever was released, after the bike had run for about a minute I stopped the engine and some 30 seconds later there was a pool of oil under the bike at the rear of the primary case, not a few drops of oil but a pool of oil I would say about a desert spoon full.       

[Topdad]

Hi re the oil leak, how much are you putting in? I was plaqued by a leak from there but found it was self inflicked ! I'd top up with oil to make up for that which I'd seen come out on the previous ride . Trouble was I'd not used the level screw to get the first level right ! The old girl was throwing out the excess . I remembered ,eventually, got the level right and nothing but the odd drip now and I don't even have the felt fitted at all . Worth checking ,the screw is the one under the footrest approx where the curve of the cover starts to move up, oh there is drain screw as well and I can't remember which that is about 2 down I think. Can't help with the 6 spring clutch ,I threw mine in a cubboard  10 yrs ago and luckily can't find it now , regards BobH.

[bikerbob]

I put the right amount of oil in the primary and checked it by removing the level screw which is the first one along the bottom next to the larger crankcase bolts.

[bikerbob]

I have been doing a bit of checking parts lists. Up to 1957 behind the inner primary case next to the crankcases there is only a gasket but on the later parts list 1958 onwards there is listed a distance piece part No 42-7518 and 2 gaskets but both list a distance piece part No 42-4792 that goes between the inner primary  case  and the frame below the clutch. Now why did BSA make that change at the front of the inner primary case as both 57 and 58 models still were fitted with the six spring clutch. My bike has the distance piece and 2 gaskets fitted at the front but no distance piece at the rear next to the frame but when you tighten up the front  bolts there is no gap between the frame and the case to fit a distance piece. The marks  on the inside of the outer primary case made by the cush drive nut  could have been done years ago the nut has had a chamfer ground onto it presumably to clear the outer case. Maybe this is where my problem arises the inner case  at the clutch end is to far forward, I will have to dismantle and measure to see if there is enough clearance to remove the front distance piece and move everything back a bit.

[morris]

I certainly wouldn't remove the distance piece at the front. If you do you'll need shorter outer cover bolts, as otherwise they'll hit the crank web. I had the bolts touching the crank on mine after changing the gaskets which appeared to be slightly thinner than the ones I removed. Scary situation there!
At the same time I was doing the clutch, and found the chain wheel touching the inner case at the rear. Although they weren't originally there I added washers until I had the same distance between both ends of the chain wheel (from memory I'd say about 5 or 6).
Depending on the age of the outer case it's possible that it's the drain plug that doubles up as level plug also. In that case it's just a question of unscrewing the smaller of the two, and filling up until oil starts dripping out.

[chaterlea25]

Hi Bob,
The inner case is easily distorted an so may have taken a "set"
"Normally" the only way the crank nut can foul the outer case is if the nut comes loose
(plenty of posts here on this topic  )

If the inner case is too far out from the engine / gearbox the first thing to foul will be the primary chain on the inner case
I adjust the distance from the engine /gearbox by adding or removing gaskets or a thinner spacer as required

The "variable" is usually the clutch centre taper and no way of really altering this except to try different ones
I then align the engine sprocket to the clutch chainwheel, shimming or machining as necessary
Then strip the clutch off and fit the inner case  loosely, refit the clutch centre and move the inner case onto the scroll and do a rough measure as to what spacers /gaskets are needed
Add the gaskets and spacers and refit the inner case and centre and check that it is all free to rotate
Alter spacers/gaskets if needed, then assemble clutch and primary chain and keep checking that all is ok as you go
Yes, check front screw length before final fitment, remembering that the crank's closeness to the case changes with the crank position

HTH
John

[BSA_54A10]

Hi Bob,
The inner case is easily distorted an so may have taken a "set"
"Normally" the only way the crank nut can foul the outer case is if the nut comes loose
(plenty of posts here on this topic  )

If the inner case is too far out from the engine / gearbox the first thing to foul will be the primary chain on the inner case
I adjust the distance from the engine /gearbox by adding or removing gaskets or a thinner spacer as required

The "variable" is usually the clutch centre taper and no way of really altering this except to try different ones
I then align the engine sprocket to the clutch chainwheel, shimming or machining as necessary
Then strip the clutch off and fit the inner case  loosely, refit the clutch centre and move the inner case onto the scroll and do a rough measure as to what spacers /gaskets are needed
Add the gaskets and spacers and refit the inner case and centre and check that it is all free to rotate
Alter spacers/gaskets if needed, then assemble clutch and primary chain and keep checking that all is ok as you go
Yes, check front screw length before final fitment, remembering that the crank's closeness to the case changes with the crank position

HTH
John

And despite what the parts books say there are at least 10 different clutch centres and many of them the only difference is the size of the hole so some will sit in a lot further than others.
because the tapper on all BSA mains shafts ( except the plunger ) are the same, any center from any bike A, B or M will go on the shaft and the 6 spring clutch was fitted to all of them.
the tin primaries had a different centre as did the bolt on primary as did the cast in primary.

[bikerbob]

Thanks for those replies I think I have solved the problem. The oil was definitely coming from the primary case, the rear clutch plate behind the sprocket was catching the sliding plate rivets but I could not move the inner case back to allow clearance.So today I decided to strip the whole primary side down to see why the inner case would not move back. The bike has a fully enclosed rear chaincase therein lies the problem the front section of the chaincase that goes around the gearbox was stopping the innercase from moving back, the sliding plate bolts fasten to that part as well. So I removed the entire chaincase and then offered up the inner primary case and it fitted much better with plenty of clearance to fit a distance piece between the frame and the case at the rear. On examining the the front section of the rear enclosed chaincase it fitted perfectly around the top of the gearbox but was not fitting around the bottom it was hard up against the part where the blind bush for the gearbox layshaft is. I cut it out to clear this also I cut some extra clearance around the swinging arm as it was not central around the gearbox mainshaft now with that loosely fitted the inner primary case goes further back thus giving adequate clearance for the rear clutch plate which does not now catch the rivets on the sliding plate. The reverse scroll on the clutch sleeve is now in a better position as before I think it was to far back into the sliding plate and I suspect that is what was causing the oil leak. I hope to get it all back together this weekend and fingers crossed no oil leak. I have also took the opportunity of modifying that rear fixing on the inner chaincase I have tapped the hole in the chaincase and made up a new bolt to suit so no fiddling around trying to get the nut on the back. Thanks again for all your input.

[Beezageezauk]

Hi Bob,

Let's hope you've sorted the problem eh!!

John and Trevor,

I've experienced the problem regarding the different tapers in the clutch centres and wondered if the correct one for a particular set-up could be established by measuring the amount of thread sticking out the end when the clutch centre is in position.  Too much thread showing if it goes on too far and not enough showing if not far enough.  All we would then need to know is the correct measurement.  Does that idea make sense to you guys?

Beezageezauk.

[bikerbob]

Got the bike built up today but things still not OK no oil leak but the clutch is not freeing off enough to allow gear change.  Can get first gear but cannot change up. All gears select OK with the bike stationary and not running but will not change out of first gear when running.  Before I stripped it down I could select all gears as I rode the bike but the clutch was dragging a bit I adjusted it and it was OK. Now I have replaced the 2 badly worn friction plates and a new chainwheel so all the plates are like new. I have adjusted the clutch as per the book tightening the six nuts so that the lock nuts have just got a full thread then using a pointer fastened to the inner case trued up the pressure plate, slackened the cable off and adjusted the adjuster in the gearbox so that the arm above the gearbox has just got a very little play then adjusted the cable to give some play at the handlebar lever. If I slacken off the six adjuster nuts I will not have a full lock nut on the threads. Could it be the springs I would have thought if it was them and they had weakened over time then the adjuster nuts would screw further on. When you pull the clutch lever in it does not feel as though it is freeing the clutch properly it feels as though it needs to come further out. I am a bit puzzled as to what to do to fix it. What is the correct length for the springs they are part No. 66-3800

[Triton Thrasher]

Sitting with engine idling, it will go into first gear, but once you move off, then changing up into second is impossible?

Doesn't sound like a clutch problem.