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Re: new clutch options

When I did BSA singles for a living I gave away every six spring clutch I was unfortunate enough to get when I purchased job lots of BSA parts as IMO they are a very poor design...
I know others have different opinions but I think the clue comes from BSA themselves...When they took over Triumph in the 50's they immediately replaced their own 6 spring clutch with the Triumph 4 spring type and all subsequent BSAs used that or a variant of it..I could detail what I consider to be the weak points of the BSA item when a comparison is made..

I got some replica parts from Dragonfly to refurbish a standard clutch on a friends bike and frankly some of it was rubbish...When ordering, in response to my enquiry about the origin of the clutch sprocket the seller confirmed they were made by Velocette Engineering in Coventry.. On receipt of the parts I could plainly see the differences between the Velocette part and the one supplied and this part, at least, I suspect was of Indian origin...It required some remachining and a lot of wasted time to get it to work correctly..

I think it is best to use either NOS parts if you can find them with a Velocette Engineering clutch sprocket if you can find a supplier...There are also some well manufactured parts from the Netherlands to replace and upgrade the originals..

Alternatively, the easiest solution is to fit a complete Triumph pre unit clutch...

Points to note here...You will need the modified clutch sleeve/adapter that enables you to fit the clutch to an early BSA such as the M20...
You will need a new clutch pushrod..This is easily made from a standard (13") length of 1/4" dia silver steel, easily obtainable from engineering suppliers..
There are two lengths of Triumph clutch springs...One is short and 'heavy', one is longer but 'lighter'...Use the longer one for nice light clutch operation.
Don't buy a clutch with a 'shock absorber' centre...There is already a shock absorber on the crank shaft. Buy the much cheaper non shock absorber type..
You will need the gearbox main shaft nut and washer that is fitted when the clutch is used on a BSA, not the Triumph one...
Buy your parts from a supplier that sells parts made by L.F. Harris...The quality is always good...
I could recommend Monty's Classic Motorcycles in Devon...I've known Monty for years and his service is excellent...Also he knows what you need as he's sold a number of complete clutches to me!....Feel free to mention my name if you do use him...Ian

email (option): ian@wright52.plus.com

Re: new clutch options

I've just noticed you are in the USA...There'll probably be a supplier on your side of the pond that can supply the Triumph parts, but my notes on the details still apply!...However, in the USA 'silver steel' is called 'Drill rod'...Ian

email (option): ian@wright52.plus.com

Re: new clutch options

Yes the design of the 6 spring clutch leaves a bit to be desired, particularly as the drum itself has to slide off the heavy backing plate.
However when set up correctly and you need a dial guage to do it.It is a magnificant clutch to use.
If you examine the "new" Burman clutch that was released just before BSA did the 6 spring, it is fairly obvious it was a copy, varied just enough to avoid a patient breach court case.
As for the TriumpH clutch, it is simpler to make & works better so it was a no brainer to tool up to make a hub to allow it to fit onto the BSA main shaft.

I often wonder if BSa bought the clutches from Triump or BSA took over making them & sold them to Triumph

email (option): bsansw1@tpg.com.au

Re: new clutch options

thanks for all the info, i will call Les and see what he has in order to keep it original but i like the idea of the Triumph set up
what is the rough cost for the complete Triumph set up Ian....ps im in Canada near Vancouver :)

email (option): taybrig@shaw.ca

Re: new clutch options

why do you remove 2 plates Ron, doesnt it affect slipage?

email (option): taybrig@shaw.ca

Re: new clutch options

Some pattern fibre plates are thicker than the originals so a full stack (8)leaves insufficient space in the clutch basket for them to separate completely when the clutch lever is pulled in..Removing two plates (one steel and one fibre) restores the overall height to within limits and allows the clutch to operate correctly. It doesn't affect grip...The fibre plates should be .093" thick when new...

It can also help with a clutch that has standard plates fitted but has wear in the various components leading to a loss of lift/misalignment resulting in poor separation of the plates...Ian

email (option): ian@wright52.plus.com

Re: new clutch options

What are the "6 spring haters" think of the pre war 6 spring clutch? Does all these bad words apply to the pre war one too? I have to decide whether restore my M22 original clutch or convert.

email (option): kalle.tikas{ät}gmail.com

Re: new clutch options

In my opinion your M22 should have the original clutch...

Actually I think the 6 spring clutch is in basics a sound design, with the chainwheel incorporated within the clutchplate pack which gives a solid unit when the spring pressure is on and has a good way to adjust springpressure and square lifting, it is only too light and cheaply made.

The single spring is in my eyes the opposite, strongly made but in basics a poor design, it is not a solid unit when the spring pressure is on, the chainwheel/basket 'rocks' around the solid clutchplate pack, this results in relatively quick wear of the outer clutchplate lips as they will hammer against the basket in both directions every time the powerline is reversed. The greater the play the harder the hammering.

Additionally no way to adjust the springpressure or rectify uneven lifting....:slightly_frowning_face:

Cheers, Michiel :relaxed:

Re: new clutch options

kevin
why do you remove 2 plates Ron, doesnt it affect slipage?
Kevin the friction plates in both my clutches are standard thickness and both clutches are in reasonable order. But it suits me fine to leave two plates out to give a much lighter clutch with more separation in the basket. As I said, both my engines are more powerful than standard and I've never experienced any clutch slip. Ron

email (option): ronpier@talk21.com

Re: new clutch options

['it is only too light and cheaply made...']

Well, that pretty much says it about the six spring clutch...It is poorly made and not typical of BSA products of the period..

There is also a tendency for the spring studs to break away from the centre, the double 'captive ball bearing rings' are weak and the material of the clutch centre is too thin and therefore only bears on a short length of the clutch sleeve spline resulting in premature wear of that part..The original cork basket inserts are also prone to falling out and are awkward to replace... I have also found that if you do have to take one off for any reason it is always a battle to set it up again...

It's not a case of being an irrational '6 spring hater', simply a recognition of the fact it isn't a very good clutch...Why bother to deal with all these issues when the better Triumph clutch is readily available?...

The fact is you can't see the clutch inside the primary covers so originality just for the sake of it on an important working part of the bike is rather pointless...Jelly batteries and solid state regulators don't seem to cause a problem in this regard, what's the difference?.... Ian

email (option): ian@wright52.plus.com

Re: new clutch options

In the past i installed the 15 spring clutch from thb support in holland.
It is very easy to mount and it can even run in oil as the plates are kevlar....and the clutch is much lighter to operate.

Re: new clutch options

http://thb-support.nl/webshop/product_info.php?products_id=37

Re: new clutch options

Hi, does this kit you buy in the Netherlands need no modification? Is it possible to dismantle the old clutch and mount it?
It seems to me an excellent and lasting solution

email (option): bongiovanni1988@libero.it

Re: new clutch options

Hi Ron

replacing the plates ect with origin unknown do you have to replace the clutch rod ?

is it the case you need a longer rod when omitting 2 plates ?

Re: new clutch options

Kidderminster Motorcycles supply the complete 4 spring clutch with adapter to fit M20.
I will be going that route.

Re: new clutch options

Roy, so long ago I can't remember about the length of the rods. If I replaced them at the time, I would have made a 1/4" length of silver steel into the desired length before hardening and tempering. A friend of mine is complaining that his clutch is heavy, so I'll be assisting him with it......Maybe the cable just needs oiling....Otherwise we'll probably remove two plates and I'll see if we need to shorten the push rod? Ron

email (option): ronpier@talk21.com

Re: new clutch options

Thanks Ron

would you know if the surflex italian made plates are any good ? reading through some post most of the plates on the market seem to be from india and of poor quality .

I also need a spring ( single spring ) again i prefer a quality one

Re: new clutch options

I would first phone Les at Russell Motors. Best times to try= Tue-Thur 10-4

Ron

email (option): ronpier@talk21.com

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