I have never seen any M20 that would go faster than 55 MPH. And I have never seen a M21 go faster than 60 MPH. And I have seen and ridden a number of them.

This applies to bikes in factory condition. No modifications to the motor or gearing. When I hear claims of faster speeds, I think it is made up or they have a speedometer that is not accurate at all. Those that claim their M20 can do 70 MPH with only 13HP, it is impossible!

For comparison a BSA B31 with twice the HP of a M20 can only do 70 MPH.

Actually Jan/Lex. cm is for dressmakers. Engineers use mm :innocent: Ron

email (option): ronpier@talk21.com

I know, I know... 😊

@ Cosimo, is this the information that you were looking for...?

email (option): wd.register@gmail.com

Centimetres???
I’m neither French or a dressmaker.
MM’s or inches thank you.

['Engineers use mm... Ron']..

Engineers use Imperial measurements...:laughing: ....Ian

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

Have you met any young engineers lately Ian? My middle aged son thought I was talking gibberish when I told him my Wrangler jeans used to cost £1 9s 11d or near enough 30 Bob. Ron :thinking_face:

email (option): ronpier@talk21.com

My M21 used to do an indicated 64. Once the speedo was rebuilt it regularly clocked 81. When I get it back from the menders[again] it will be interesting to see how fast it goes

Well it won't do 81mph without some serious surgery:relaxed: ...My 720cc 'M20' which is standard apart from the capacity boost, changes to gearing and an M21 carb has been clocked by a car at 78mph but frankly there wasn't much, if anything, left performance wise...
Young engineers?...Not many of them about Ron..Apart from the fact our manufacturing base has virtually gone the 'youf' haven't got time to look up from the social media accounts on their phones as they check out their 'today' photos on Tic Toc..:laughing:..Addiction is indeed a terrible thing...Ian.

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

From someone who uses mm’s and inches, it is surprising how many BSA’s seem to have my creations on them.

Worse so,is the fact I make English parts here in the Antipodes.

email (option): wd.register@gmail.com

"Fascinating stuff, this Imperial system... Blame Napoleon and the fact that we have 10 fingers on our hands for the Metric System. Less fun... 😁"

I used to wonder if there was a time when it was common for some people to have 6 fingers and toes on each hand and foot Jan?

Mark

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

Have a look at this Mark! 😃

email (option): wd.register@gmail.com

'If it ain't broke don't fix it'....Ian

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

Interesting info Jan. Can anybody explain the discrepancies in the measurements of the left & right turning circle's?

email (option): fuzzyempire@hotmail.com

Possibly it's because the left fork leg is splayed out for the speedo drive? Ron

email (option): ronpier@talk21.com

Since about September last year, my Wm20 has been absolutely flying!!! When I take her out I find myself having to concentrate a lot more on holding her back, sport's car's, Honda's, Ducati's even MV Agusta's can't live with my old War horse. But then I do live in Wales and there is a blanket 20mph speed limit. So finally my 13bhp can blow em all away 😂

Thanks Jan, that answers many questions.
Not so good for french relations!

Mark

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