MC18 Mk1, MC18 Mk2, MC21, and MC28 will all swap into any post 1988 frame, with only a need to hook up the correct wires from the stator/regulator etc., and lengthen/shorten them as necessary.

The only motor that is not a direct fit into any other frame is the MC16 motor, as it has solid engine mounts.

All barrels and heads are interchangeable. Just use matched barrels and heads if you don't know exactly what you are doing! For example, use MC21R barrels and heads, or R2J barrels and heads, or even MC16 barrels and heads* etc... but do not mix them up. (You can even run an MC18 setup on one side and an MC21/28 on the other, on ANY cases if you wish, with little or no consequence.)

*MC16 barrels have significantly smaller exhaust ports than all the other models, so don't use them unless (a) you're restoring an MC16, or (b) you have no other alternative in the short-term.

There are plenty of posts in the forum archives over the last 10 years concerning cranks, transmissions, clutches, engine/frame, ignition, flywheel, etc. compatibility. Most of it will work with very little fiddling. It's all pretty straightforward once you have the parts in your hands! The motors, carbs, transmissions etc., were all relatively unchanged from 1988 through to 1996. Unlike some manufacturers, Honda got it right with the first design, and it's very simple to work on!

'87~'88 cranks are similar, 1989 cranks are unique, '90~'96 cranks are all the same. The cranks only fit their respective cases. As a general rule, HRC RS250 cranks ARE NOT a direct fit into the NSR cases.

The rest you can look up!
_________________
Andy.
NSR-WORLD.COM

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