In my quest for speed, i am interested in fitting an m21 crankshaft and piston into my m20 is there a certain crankshaft that i should use or are they all interchangeable.
I recentley fitted diffrent cams no real gain in power untill the revs build up.
I have had the bike rebored and now getting the top speed i was after 55/60 not after going any faster it just seem like every where i go there are hills a bit more low down pull would be nice now.
Thanks for any info
Hi Steve...The bikes looking nice...The M21 crank will fit straight into you M20 without any modification...
Removing some material from the rims and/or sides of the flywheels can be beneficial to help it rev a little more readily...If you do that it is better to use the steel M21 flywheels if you can find them (forging number 66-635)
Note this flywheel set was also used for other engines (M20,B33,M33) with different strokes so check they are in fact 112mm strokeif you come across them..
The more common flywheels are the cast iron ones...These have numbers beginning with 7..e.g. 66-775...
You may well find the standard M21 set up will give you what you are looking for however...
You will need the appropriate M21 piston to go with the flywheels..(or a 'long rod' B33 piston to give you 635cc)...
M20 and M21 conrods are the same...Ian
Thanks for the reply Ian, off to see a guy next week with a m21 crankshaft and all been well things will work out well :)
you might not like this but also having ago at building a bike very much like this one .
I like the 'chunky' style..and you can't dispute older boxers are pretty simple and hard to break or wear out...and that has to be good..
I don't think I'd be heading for the nearest field in a hurry with that lump though..
....
Motorcycle wise I like some variety and am always interested in what is being built...Design trends and fashions over the last 40 years are something I study very much...
The current wave of Bobber, flat tracker and café racer building is a good thing in my opinion and I think reflects to a degree some disillusionment with the weight, cost and technical complication of what the manufacturers are currently offering...
If that leads to the acquisition of skills, self expression and a second life for some worthy bikes that were destined to end up in the breakers I'm all for it...Ian
email (option): ian@wright52.plus.com
I know it well from my youf...Haven't been that way for a few years though...Ian
email (option): ian@wright52.plus.com