The "problem" with the 1989 MC18 is that it shares the same centre crank bearing/seal as the MC21 and MC28, which is prone to premature failure. If you don't really know your stuff, then I say it's imperative that the bike starts from stone cold very easily. If it takes continual kicking over, then I would be wary. Irrespective of how it starts however, unless the seller has a verifiable receipt for either a new crank or a refurbished one within the last 6 months, be prepared for a engine tear-down and a new bottom-end.

Sorry to sound all doom and gloom, but the centre seals just don't play at all well with fuels with ethanol content, and it's now my biggest concern with later models.

The rest of it is pretty much common with all bikes of a similar age. Have a good look at the chrome on the forks & rear shock for rust, pitting, and traces of oil. Check the brake pads (particularly the rear) and discs, and the condition/adjustment of the chain, as they all tend to be good indicators of previous levels of care/maintenance.

With the motor running, it needs to have a nice smooth idle at around 1200rpm. Blip the throttle, and it should instantly return to an even idle. If the revs "hang", or the idle is erratic, it can be a sign of a bad crank seal. When blipping the throttle, check to see the RC Valves (powervalves) operate. It's unlikely they will operate as you expect... unless you rev the motor quite high, it will appear that the RC Valves open and then immediately close again (unless you rev it past 8000rpm -- but I don't expect the seller to be too happy if you try revving the motor like that!). This is normal, as the RC Valves open at 2000 for setting purposes, then close again at around 3000rpm.

And have a good long chat with the selller! Does he show a good knowledge of NSRs and the community, and inspire confidence, or is he just trying to cash in on the 2-stroke gold rush?!
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Andy.
NSR-WORLD.COM

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