Not necessarily a new crank, but new seals.

The smoke will likely be quite white or grey if it's drawing in oil from the transmission.

You can actually replace the seals with the motor still in the frame if you want. It's a little tight, but easily done. You do have to split the cases and take the crank out to do it though.

Check the main bearings by hand to see if any of them "feel" rough or notchy. If you can feel any resistance or play at all, then that particular bearing is shot. Make sure you replace all 3 seals (R5K, MC21, MC28 have a rubber O-ring seal around the centre bearing).

If you are lucky, and it's just a seal, then it's not expensive at all. A couple of base gaskets, a couple of piston circlips, a clutch cover gasket, and the seals; although it probably wouldn't hurt to at least put a new set of piston rings in too, while you've got it all apart.
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Andy.
NSR-WORLD.COM

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