I don't understand why you would want to fit an MC18 swingarm to an MC21. The MC21 Gull-Arm is (a) significantly stiffer, and (b) gives significantly more room under it to run expansion chambers... something you will surely need to consider if you are thinking of running "GP style" pipes on the conversion.

Go search "Wyn Belorusky" on Google and have a look at his RZ500. Although he uses a modified RZ frame and a TZ (or maybe 3XV, I can't remember... it was 10 years ago I last saw him and the bike!) swingarm, you can see the benefit of plenty of clearance under a "gull-style" arm that an MC18 arm won't give you.
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Andy.
NSR-WORLD.COM

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