Questions? Looking for parts? Parts for sale? or just for a chat,

The WD Motorcycle forum


WD Motorcycle forum
Start a New Topic 
Author
Comment
Engine sprockets. 18T to 20T

Hello all.
Ref my 1943 WM20. I am going from a 18T to a 20T engine sprocket. I understand I need to change from my 69 link primary chain to a 70 link chain. Any idea where I can buy a chain from. Draganfly are out of stock.

Thanks Colin

email (option): colinmbrindley@btinternet.com

Re: Engine sprockets. 18T to 20T

Your local bike shop may be able to help if they are open...The primary chain size is still in common use on modern machines....

It's 1/2" x 5/16" chain or '428' in modern parlance I think...Ian

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

Re: Engine sprockets. 18T to 20T

I've used this guy. He knew what to supply for Lex's 1940 WD/C. Ron
https://the-chain-man.co.uk/

email (option): ronpier@talk21.com

Re: Engine sprockets. 18T to 20T

Is that correct, Ian ??

I have 1/2" x 0.305 for the primary....seems a fraction more narrow than 5/16".....??

Re: Engine sprockets. 18T to 20T

That's right Michiel...It always seems to get 'rounded up' to 5/16" in modern descriptions of the size.....Ian

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

Re: Engine sprockets. 18T to 20T

OK, clear, thanks!

Re: Engine sprockets. 18T to 20T

5/16" is the distance between the plates. The old talk of measuring was the roller width .305". Ron

email (option): ronpier@talk21.com

Re: Engine sprockets. 18T to 20T

Thanks for info Ian. I have ordered one on line.

email (option): colinmbrindley@btinternet.com

Re: Engine sprockets. 18T to 20T

[5/16" is the distance between the plates. The old talk of measuring was the roller width .305". ...']

Thanks Ron...I didn't realise that...I thought it was just 'loose talk'...:relaxed: ....The learning goes on....Ian

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

Re: Engine sprockets. 18T to 20T

Why would you go for 20t . I mean coming from 18t seems a big step to me. Besides IT is not in any manual known to man.
For a while I used 20t (g.box 19t) but did not work for me. No acceleration from standstill. 😭

John

email (option): john.kater@chello.nl

Re: Engine sprockets. 18T to 20T

When I increased my engine to 600cc I tried a 21T sprocket, but it was too tall for my likings so I dropped it to a 20T. 20T may be too tall for a standard M20, especially if you ride around a hilly area. I think 19T is the size for a standard civvy M20. Ron

email (option): ronpier@talk21.com

Re: Engine sprockets. 18T to 20T

When comparing 'civvy' and WD M20s don't forget the 'civvy' has a 19T gearbox sprocket as standard and the WD models an 18T...Ian

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

Re: Engine sprockets. 18T to 20T

Forgot to mention that I have an 18T engine sprocket. Feels much better than 19T 👍

John

email (option): john.kater@chello.nl

Re: Engine sprockets. 18T to 20T

I usually raise the gearing on my bikes, even with standard engines, because I like the characteristics of 'taller' gearing...The original gearing, after all, was only a 'one size fits all' compromise arrived at by the manufacturer...

For example, I always run standard B33s on a 21T engine sprocket instead of the standard 19T...
When it comes to standard M20s I think there is a problem with the lack of available power and care must be exercised when selecting sprockets as it is very easy to 'overgear' to the point where any hill, or even a strong headwind, will require a change down to a lower gear...

One odd thing I have observed though is that not all M20s are the same...They should be but they're not...Some seem to go better and have more power than others even with a standard engine...I can't explain that in detil but based on observation and anecdotal evidence it seems to be the case...

With that in mind and the different riding conditions and requirements of different riders I think some experimentation is the only answer unless the standard set up suits you...I don't think it is possible to generalise and say '*** is the best gearing for every rider (or bike)'...Ian

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

Re: Engine sprockets. 18T to 20T

So the reasoning behind me trying this is curiosity. Currently I have 18T engine and 19T gearbox. When I set off in 1st gear I am changing up almost immediately as its feels too low geared. I can actually set off in 2nd without any problem. Along with the engine racing(to my ears) at 45 mph. I would like to lower the revs at this speed not necessarily increase the top speed. Now if it works , it works. If not I will change it to a 19T engine. I`m also not sure whether weight of rider makes any difference but I`m built for speed at 65kg myself. We do have hills in Derbyshire where I live but I tend to head towards Lincolnshire for ride outs as the traffic is better. I have read every old thread on this subject but there`s nothing like trying for yourself as Ian says they are all different.

email (option): colinmbrindley@btinternet.com

Re: Engine sprockets. 18T to 20T

Yes, just try, with the nice shock absorber unit BSA has, changing the sprocket is very easy. Great system! :+1: :+1:

Re: Engine sprockets. 18T to 20T

The M20 and most British pre-unit bike primary chains are not 1/2" x 5/16 (.335" roller diameter) which would be a 428 chain.

The correct designation for a M20 and many other bikes is a ISO 08B-1, which is 1/2" x .306" (.335" roller diameter). So the same other than it is .0065" narrower. It is technically considered a metric size chain.

I have also seen in the USA people attempting to use a #40 chain which is 1/2" x 5/16" but has .3125" rollers.

Also avoid at all cost modern made Renold chain at it is junk. If it is not stamped on the links "Renold England" it could have made anywhere, probably China and won't last long.

If you order from the CHAIN-MAN in the UK you will most likely receive a German IWIS chain which is very good quality.

Bruce

Re: Engine sprockets. 18T to 20T

Can I just check a couple of things Bruce. The designated primary chain for an M20 is 1/2" X 305 (305 and 335 being the Width & Radius of the rollers) which is actually .0075" (7.5 thou) less than the 5/16" between the plates. So 1/2" x 5/16" seems to be the designation used by modern chain suppliers including Jason "The Chain Man". I just bought one off him for Lex's WD/C... What is the metric equivalent of .305" (7.74mm??)

Ron

email (option): ronpier@talk21.com

Re: Engine sprockets. 18T to 20T

['Also avoid at all cost modern made Renold chain at it is junk. If it is not stamped on the links "Renold England" it could have made anywhere, probably China and won't last long....']

Forgetting the debate about the exact sizes I use Regina chain and get good service from it...Ian

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

Re: Engine sprockets. 18T to 20T

Renolds has production plants in China and India which they own...That doesn't automatically mean a drop in quality as the process and standards will still be controlled by Renolds...

If everything produced in China was rubbish Harley Davidson, Triumph, BMW, Bosche etc. etc. would also all be producing rubbish...

The chains can't be marked 'Renolds England' if they are not manufactured in England...If there has been a drop in quality, which is debatable, then it's a choice made by Renolds, not the result of where it's manufactured, as they aren't just buying chain in from far Eastern manufacturers.... Ian

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

Re: Engine sprockets. 18T to 20T

Confused.com
So would a DID chain made in Japan 428 not be correct then ?

email (option): colinmbrindley@btinternet.com

Re: Engine sprockets. 18T to 20T

I thought you'd say that Colin after I read the last few posts...This is a discussion on minor details that make no practical difference....Go ahead and get the chain...it will run fine without any problems...:relaxed:...I've run 428 chain for decades as have many people..... Ian

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

Re: Engine sprockets. 18T to 20T

Cheers Ian. Its on its way.

email (option): colinmbrindley@btinternet.com

Re: Engine sprockets. 18T to 20T

When BSA made your M20, it did not have a 428 chain. The same applies to Triumph, Norton, AJS/Matchless and others. If they used this size chain, it was 1/2 x .306".

Now having said that, a 428 chain will work fine. The small amount it is wider will not cause any problems. You will also see the 1/2" x .306" chain commonly marked as being 428 even though it is not. So what size chain will be sold to you can only be determined by measurement.

No on the subject of modern Renold chain, the motorcycle stuff is junk. It is an industrial grade chain which is made to a lower standard than the old made in England chain. This is not a personal opinion, I have been told this by someone in the industry. On a low power bike like a M20, perhaps it does not matter. On something like a Triumph 650 that is ridden fast, that chain will last nowhere as long as the old stuff. If you check the Renold website, they do not even list any motorcycle chains as being made by them. With the disappearance of the British motorcycle industry, there is no money to be made by Renold in producing the chain anymore. I suspect that like modern Lucas parts they are licensing the name to whoever pays the fee.

Bruce

Re: Engine sprockets. 18T to 20T

Thanks for the confusion Bruce. I do agree with your comment on "made in China" after working there over a period of the last 8 years and some 20 plus visits to factories where I fitted UK built ultrasonic rail inspection systems on to their trains. I will say however they learn at a lightening speed and absorb everything the foreigner teaches them, that is their culture. Their high speed trains are superb and I wish we had them in the UK. Ok they were taught by the Germans how to do it but they work a damn sight better than our train system.

email (option): colinmbrindley@btinternet.com

Re: Engine sprockets. 18T to 20T

Well, tried a test run yesterday and 20T engine sprocket works for me. 1st gear is more useable, no clutch slip and more than enough acceleration. 4th is less busy at the same speeds.

Nieuwe pagina 1