The clutch tool can be fabricated from an old steel clutch plate. See the topic/post here:
http://nsr250.net/forums/viewtopic.php?p=104915#104915
If there's corrosion on the crank from water damage/damp, it's almost certainly scrap I'm afraid. Officially NSR250R cranks are (were) classed as a consumable item, and therefore non-rebuildable. Some OEM parts have become available (the Koyo main bearings) in recent years, and some owners have managed to adapt third party parts such as big-end bearings and thrust washers, but none of these are available officially from Honda. The biggest problem though, is that the main bearing pins are integral to the crank flywheels, and cannot be replaced. Any pitting whatsoever on the pins (which is highly likely if there's corrosion on the crank) renders a rebuild unviable.
1989 R5/6K cranks are similar to MC21 and MC28 cranks, but not interchangeable. It is possible for a good machine shop to turn down a new MC28 crank to fit in 1989 cases, but it's not recommended as the cranks are obviously balanced at Honda, and you always run the risk of getting swarf in the bearings, no matter how careful you are.
Don't just let any old muppet rebuild it! They need to be experienced with NSR cranks.
Fingers crossed, when you split the cases, the crank [at least outwardly] appears in good condition with no immediately apparent corrosion. It will need rebuilding though, that's a given.
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Andy.
NSR-WORLD.COM
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