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Clutch Spring & Cush Drive Spring - BSA M20

Hi
Original springs are becoming harder to find & those which are available at times are not the best from discussions with some other forum members
The material for these “square” wire springs is becoming more scarce & expensive - so many replacements are now made with round wire - although BSA did provide some round wire clutch springs towards the end of production of the M21

I am looking at the possibility of having springs made with correct square wire & to original specifications
If anyone is interested- please drop me an email so that I can guage interest to establish numbers and to allow for a quote from the maker

Br
Jo’b

email (option): jonnyob1@googlemail.com

Re: Clutch Spring & Cush Drive Spring - BSA M20

I went to fit one of those (Russells) new round wire springs to a friends M20 last week, but it fell through my ring compressing tool and I had no other means to compress it, so I fitted the old one which is working fine. A batch of the original type would not be a bad idea John. Ron

email (option): ronpier@talk21.com

Re: Clutch Spring & Cush Drive Spring - BSA M20

The 'square wire' springs were only used with the 4 lobe shock absorber assembly...
When BSA changed to the 2 lobe assembly they also changed to the 'round wire' springs...The 2 lobe assembly had much larger radii on the cams to smooth out the operation of the shock absorber..This meant that the cams moved more easily against one another, so the round wire spring was made substantially heavier to allow it to control the movement...

With newly manufactured springs I would imagine whether the spring is 'round' or 'square' doesn't strictly matter as long as the essential dimensions and, more importantly, the poundage conform to the original specs.. Worth enquiring about that with the manufacturer if it affects cost greatly....When original springs are used the correct spring should be used for the cam type to achieve correct operation. They should not be regarded as interchangeable...

The 2 lobe cams are substantially wider on the operating faces than the 4 lobe version to reduce wear but what is not so obvious or commonly known is that there are two versions of the 4 lobe cams as well, with later ones being a little wider than the early examples for the same reason. Those are worth looking for when the 4 lobe version is used...Ian

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

Re: Clutch Spring & Cush Drive Spring - BSA M20

Just to be clear, I was referring to the clutch spring. Ron

email (option): ronpier@talk21.com

Re: Clutch Spring & Cush Drive Spring - BSA M20

John mentioned both in his post heading...I only referred to the shock absorber springs in my comment.....Ian:relaxed:

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

Re: Clutch Spring & Cush Drive Spring - BSA M20

Hi John, Great intention to make parts available again!

But remember there is already a very clever alternative for the clutch spring available from THB Support which tackles the occasional tilting problem with the original spring: Multiple small springs placed in a circle which guarantee a straight lift.

I have to admit I have never tried one myself but heard good reviews about it....

BR Michiel

Re: Clutch Spring & Cush Drive Spring - BSA M20

The Cush Drive springs 15-46 made its first appearance in 1923 on 2 3/4HP flat tankers.
And is used on all models except 250 and some V twin.
They used a shouldered nut that only work with square material not round, and a lock nut.
Also they at first use a six lobe sprocket.
These can be replaced with a four lobe with has the same bore.

Re: Clutch Spring & Cush Drive Spring - BSA M20

Hi all
The spring manufacturer has sourced “square” section wire but is obliged to buy 200kg at a time which means from a commercial venture, it makes no sense for him
It leaves us riders potentially with a problem for future in the availability of such important components - no springs - no go
However - he has sourced a limited quantity of round wire which can be adapted / modified & finished to that of the “square” section we are used to & fit into the clutch tool mentioned on other threads on this forum - your tool Michiel
Dimensionally the same - but still round section
Of course price is dictated by volume ordered but if ordered in quantity - I expect pricing to be a maximum of £15 per spring
I would be doing this as a one off order
If you are interested- please contact me with your interest & quantity required - this isn’t a commitment to buy but to guage interest & obtain more clarity on final pricing
To clarify this is for
Clutch Spring
Cush drive spring

Darren
He has an nos Cush drive spring from me - if this spring needs to be further modified it can be done to match existing securing methods
These springs will fit other bsa models - more knowledgeable people than me will know
Br
Jo’b

email (option): jonnyob1@googlemail.com

Re: Clutch Spring & Cush Drive Spring - BSA M20

Hi all
Based on the low level of interest in getting springs made, I will not be proceeding with getting these done
Thanks to those who did contact me on this
Br
Jo’b

email (option): jonnyob1@googlemail.com

Re: Clutch Spring & Cush Drive Spring - BSA M20

This is always the danger John, I never worry if the parts I make will sell. Most people don't buy in advance, only when they want it.

email (option): pes.sales@btconnect.com

Re: Clutch Spring & Cush Drive Spring - BSA M20

i have the cush drive nos complete and the spring also
if anyone interested i hope i can help
cheers

email (option): sl_hussein@yahoo.com

Re: Clutch Spring & Cush Drive Spring - BSA M20

Some one must be making square section springs because I bought 4 of them last year fromBill Green when he was selling down his stock prior to the proposed sale of the business which fell through.
I would guess they originated in India where he got a lot of parts made but these seemed to be good as I am using one right now & have another in the model S .
The M20 one has done quite a few thousand miles on his spring without any problems .

Re: Clutch Spring & Cush Drive Spring - BSA M20

Hi Trevor could they be new old stock as Bill sold me complete float bodies a while ago that were left behind in India by the British. He had some good bits prior to getting parts made in India. He offered me carburetter parts last year but as soon as I saw the finish on them I knew they were Indian made and inferior quality.

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