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Mar 10, 2012 - 6:31PM

Early M21 cranksaft stroke??

Hello,

I have copy of the arcticle "Going nowhere fast"(CBG, May 2002) on which is described one special M20/21 728cc sprinter. There is mentioned that early M21s have even longer stroke than normal 112mm, which could have given around 800cc.What is this special early M21 crank?

BR

paavo

email (option): paavo.vesala2gmail.com

Ian Wright

Mar 10, 2012 - 7:07PM

Re: Early M21 cranksaft stroke??

Hi Paavo..That article contained numerous mistakes on the technical side and a lot of nonsense about tuning M20s.
The 112mm crank is the longest stroke crank available for an M21..There were two..the earlier crank being fitted prewar with a 105mm stroke...Ian

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

Paavo

Mar 11, 2012 - 9:39PM

Re: Early M21 cranksaft stroke??

Hi,
I´m just curios about what is the longest stroke used
on motorcycle single cylinder engine? For Harley there are 5" stroke cranks as known but v-twins have somewhat better mechanical balance...

email (option): paavo.vesala@gmail.com

Ian Wright

Mar 11, 2012 - 10:06PM

Re: Early M21 cranksaft stroke??

Hi Paavo, The longest British motorcycle, single cylinder stroke I know of is the Norton Big 4 at 120mm...Ian

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