OK so now it is the darn clutch! this B44 has been messed with, the clutch has been modified to a 5 plate, quick and dirty as per Rupert Ratio. Standard hub, no thrust washer. It slips. Fitted new springs, fitted new plates (Surflex), MUCH worse! cannot even start the bike it slips so much. Tightened down the springs way more than they should be, got it started, but only just.

Put the old plates back in and with the screws a long way down it kinda works (still slips in top gear, wide throttle) but there is no way I can wire the nuts, screws are too far in.

Thoughts ……. the stack of plates is just too thin, so add another plate, question is which type and where? another plane plate under the first friction plate? (like the stock 4 plate clutch).

As far as I can tell I have done the adjustments right (as per Rupert Ratio)

Are the plain steel plates dead flat, could the cush drive be worn out?

Hope the plain plates are flat, they are brand spanking new! Not sure about the cush drive but how would than make the clutch slip? I meant to say in the first post is that the stack of plates do not "fill" the cage, that and the fact I have to screw in the bolts so deep that it is not possible to wire them makes me think that I need another plate in the stack.

Try putting another friction disc, even an old one, and another steel. As long as the last steel is not protruding beyond the basket, it should do the trick. I just had that same problem on the TR25 land speed bike (hi-compression piston), put in another friction and steel plate and there is no slipping now.

Tom

!Not sure about the cush drive but how would than make the clutch slip?!

When worn they tilt under load, the wear is hidden internally, if you open up the cush drive it is common to find the spider vane has chewed into the retaining endplates. All parts of a clutch wear, this part gets overlooked very easily.

Plus 1 to both Gavins comments. Had I not seen his post I would have stated the same. Any wear in the hub and you can waste a lot of time and money elsewhere. These standard clutches are actually really good for the unit single.

It might be worth stripping and rebuilding the hub but more often than not it’s cheaper and easier to buy a new one.

I like gavins answer
, but while your checking stuff
check the primary chain alignment.
The parts book shows
3 different-width distance-pieces ...
That can be used to space out the engine sprocket .
.

What kind of oil are you using? You need to be using oil suitable for wet clutches, this usually means motorcycle specific oil with grade MA or classic car oil with a API grade no higher than SF. Using the wrong oil will definitely cause clutch slip.

OIL! ………….. on a previous request on this esteemed forum I posed this question and in the replies I had was the statement that "classic 20 / 50" was fine. Of course the devil is in the details and I had not appreciated "classic" and used 20 / 50 SN. Will replace with "Yamalube 10 / 40" (after washing the plates) designed for wet clutches, and will report back. I must admit though it does not feel right putting Japanese oil into a Brit bike, will the bike reject it like a miss matched blood transfusion??

ATF type F has worked for me.
I also had the same issue as you (lower than standard stack height) and added extra plates.

Yamalube should be fine as its designed for wet clutches, so hopefully you should see much better operation with no slippage.

I've also done the 5 plate conversion on my B44 using Sureflex plates and it works really well, the only thing I would add is to ensure the spring nuts are lock wired in place as they have a tendency to loosen after a few hundred miles.

Can't tell properly if your replies are supposed to be humerous or sarcastic, neither carry well over written text on the net...

Yamalube should be no more of a problem in the engine than the american gasoline that goes in the tank (as I say humour doesn't carry well on the net)

A classic 20/50 should be fine as long as your chosen oil doesn't have any friction modifiers in!

Also have you done anything with the clutch hub yet?

If your having to lockwire clutch spring nuts then the pip on the head is worn away or missing or the ends of the spring are too smooth and the pip is riding over the top, if this is the case a small amount of the tail on the spring needs to be cut off so that the pip locates positively, most decent springs dont have this problem but many others do.

May I add that in the case of a B44 ATF would be ok, but if it was a B50 this wouldn't be ok as the primary and engine oil are shared..

Thankfully most of our petrol still comes from Venezuela so rejection of US "Gasoline" by the bikes immune system is less of a problem than it could be.


Attacking the clutch this weekend, including the hub, lets see what happens!
I am trying to stick to a single oil for the motor and the Primary, mainly because getting these oils is not easy on a rock in the sun, so if I can find one that will do both it makes life easier and I can stock pile.
Most of our branded oil (other than the Yamalube) is "made under license" in The Dominican Republic, lord alone knows what is in it, friction modifiers or not.

+ 1
This is easily overlooked ... the stock engineering is quite simple but efficient ... as a stop nut .
the pip ( dimpled onto the nut ) is softer than the spring-end ... which means the nut has
a limited amount of off-adjustments before the PIP gets worn down .

Older stock springs , with simple diagonal cut wire ends , can be particularly rough on the pip .
The spring end will jam and not allow the nut to come off
unless the spring is compressed .
Or if the nut aggressively loosened off ... the pip wears off quickly.

And newer forged spring ends ... but may be too smooth to hold the pip .

Watching this as I've started racing a B50 and have heard the weak clutch stories. May need to try the extra 1 1/2 plate trick.
Regarding spring nuts, there were no pips on mine, only holes factory (assume) drilled for safety wire

Folks ask me lots of questions about their unit single clutch problems. I explain that just about everything needs to be looked at and should be considered suspect. Starting with the oft bend push rod.

The retaining plate with the studs for the clutch nuts came with two (perhaps three) different lengths of studs. However they never changed the part number when they made these changes. There were two different length spring cups. Earlier spring cups and spring nuts had "pips" that held the springs in place (if the springs were wound in the correct clockwise direction) Later drilled nuts were added and then later the pips on the nuts were eliminated to favor just wiring the drilled nuts. In the last few years BSA added pips to the outer edge of the spring cups and notches in the pressure plates to keep the cups from rotating.

There are issues with the length of the spring cup and the length of the springs used. On the earlier clutches with the short spring cups the springs were a bit shorter but short springs do not seem to be on the market. I do not think coil binding is a problem using the short cups but putting on a fresh set of long springs into short cups can be a real struggle starting the clutch spring nuts!! And what if used on the backing plates with the shorter studs?

The biggest mystery is the springs themselves. Currently I have bought springs from at least 6 different suppliers and all these springs have come from different manufacturers. About the only thing they have in common is the length (more or less). They are all made to the length that the last in the line springs were made (1971-73) to work with the deeper spring cups. They come wound in the wrong direction, counter clockwise, which I then toss into my big box of "unsalable crap from suppliers". They come with any where from 8 to 10 winds. and in at least a couple different wire thicknesses. In no cases have any of the folks I have bought these from been able to tell me the specs these have been made to, like what type of wire or the strength of the spring. I have found that more winds are usually softer than less winds, but not always. The springs I am talking about are all sold as standard replacements for unit single clutches. Not as heavy duty, medium duty or light duty. The ones sold as heavy duty are usually so stiff that they are not worth using unless all you are doing is dumping the clutch in a drag race.

One day I brought all these different spring types I happened to have on hand to Coventry Spares and John Healy was kind enough to play with them on his accurate spring tester. I used the long spring cup as the standard length to press all of the springs into to see their relative pressures. We came up with spring pressures from 32 lbs to about 80 pounds (some heavy duty ones!). I had more that came in at 38 lbs with 10 winds than other types. So that is what I tend to sell.

What is correct for these clutches? I have never seen if BSA recommended a specification. Does anyone know?

On occasion I have a pesky clutch that even after everything is rebuilt and replaced it slips. Surflex plates seem to be the final solution in these cases. They are twice as expensive but work well. Second favorite plates are Emgo's. Dead last (and I will not use) are Barnett plates. Too dam sticky!! I use ATF type F fluid in the pre-B50 motors in the primary case. It works fine. Other folks have different preferences.

For whatever reason I have found the pressure plate to be the least of the problems in the clutches. I'd rather spend $ 50 to $60 on fixing other problems with the clutch than on a fancy alloy pressure plate. I've had alloy pressure plates that are a bit too thick and hit the primary cover, so out they go. There are quite a few folks making these alloy pressure plates so there is likely a lot of variety in what is available on these. Sort of a CNC shop favorite I guess. No doubt others have a different opinion on these pressure plates.

Of course the 5 friction plate clutches are going to slip less than 4 friction plate clutches, and more friction plates will work even better it they can be fit into the clutch.

So these are my random observations to be added to the other suggestions in this thread.

A good and informative write up Peter

Peter,
Fairly sure I have some original unused B40GA clutch springs kicking around in one of the boxes or bits that some day I will never get around to putting together.
From memory they are 4 spring clutches.
Would that be of any use to you for a sample ?
happy to send some over or just do some testing & send you some results.
Like a lot of things I can make springs with the exact same spring rate & free length a hundred different ways

Trevor,

I'll take you up on your offer if you would send me 4 original unused clutch springs. Happy to pay the postage. Perhaps I'll do a photo essay on all of my spring results.

Peter

That's fine .
Got to have a dig through the B 40 bits soon

So ………. changed the plates back to the new Surflex (after cleaning them with a couple of cans of parts cleaner). They were quite a way short of filling the clutch basket so added 2 more old plates, one plain and one friction. This brought the stack nicely up to the rim of the basket. Installed the new springs and suddenly the instructions on fitting the nuts / screws made sense, and was able to fit leaving a coil of spring visible but still be able to wire the nuts. Changed the oil to the Yamalube for wet clutches, after cleaning EVERYTHING, that oil I was using was STICKY.

I was not able to check the cush drive, those screws must be made of the softest steel in Christendom. I will have to have replacements and new rubbers on hand before I set to again.
Put it all back together again and ……… well it was better but still a little slippy …… decided to put a few miles on it and see what happened. Seems like it needed to "bed in" as it got steadily better, maybe there were some traces of the sticky oil in the friction linings?
Thanks for all the ideas.
Still don't know why the new plates did not fill the basket though. (neither did the old ones)

If its still a bit slippy check that the clutch pushrod has a little slack in it, also that the cable has some slack.