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M20/M21 block
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Topic: M20/M21 block (Read 2261 times)
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Mike Farmer
Golden Flash
Posts: 2549
M20/M21 block
«
on:
28 November, 2017, 18:45:19 »
Just a thought. Do the M20 and M21 have identical cylinders. The reason that I'm asking is because my book says that the carb bore is different, that of course makes sense, and I am wondering about whether there is a difference in the inlet orifice.
Mike
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TTJOHN
Golden Flash
Posts: 544
Re: M20/M21 block
«
Reply #1 on:
29 November, 2017, 14:35:04 »
Not entirely sure but I do believe that they are one of the same, the only difference is the piston & piston stroke, I think they were both fitted with the same carb, 276 if I remember correctly
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Mike Farmer
Golden Flash
Posts: 2549
Re: M20/M21 block
«
Reply #2 on:
29 November, 2017, 19:45:53 »
Thanks for that. My book says for the Monobloc- M20 376/21 1"
M21 376/23 1..1/16"
However as far as I can tell the receiving orifice on the block appears to be only the one size 1.1/8".
However its really not important as its only for my interest. But I would be interested if anyone has a definitive answer.
Thanks agen
Mike
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Pete C
Silver Star
Posts: 277
Re: M20/M21 block
«
Reply #3 on:
30 November, 2017, 13:09:50 »
I think they are different but only in the size of the inlet port. As you noted the carbs are slightly different sizes. A definitive answer can certainly be got from the kindly folks on the WM20 site forum at:
http://www.wdbsa.nl/
Cheers
Pete
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JulianS
Empire Star
Posts: 2637
A10
Re: M20/M21 block
«
Reply #4 on:
30 November, 2017, 14:12:20 »
Parts book shows the same part number for both.
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Pete C
Silver Star
Posts: 277
Re: M20/M21 block
«
Reply #5 on:
01 December, 2017, 05:54:24 »
same in my parts book..I stand corrected
I have an M21 on which I think someone has previously opened the inlet out a little to suit the carb as it is more than 1" diameter.
cheers
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Mike Farmer
Golden Flash
Posts: 2549
Re: M20/M21 block
«
Reply #6 on:
01 December, 2017, 08:30:38 »
Hi
Thanks for all your replies.
As some of you may recall I 'accidently' converted mine about 12 months ago so I'm scratching around a bit.
My inlet port is 1 1/8th which is larger than either so no problem.
We'll see what happens some when down the line "if and when"
Mike
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M20/M21 block