Unless you've seized it, I highly doubt you'll need to replate either barrel... in fact, even if you have seized it, the barrels will often clean up!

For all intents and purposes, the MC21 and MC28 R motors are the same, and the MC21 and MC28 SE & SP motors are the same. Don't mix R head/barrel parts with SE/SP unless you know exactly what you are doing, and are handy with a variety of accurate measuring devices!

21 and 28 transmissions are different, but interchangeable.

If you put an MC28 motor in an MC21 frame with MC21 wiring harness and ignition, simply use the MC21 flywheel, and vise versa.

Barrels are available from Honda still... if you really want to pay about £450 each for them!
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Andy.
NSR-WORLD.COM

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