Jonny, welcome to the forum.

The NSR is a pretty reliable bike, even though its a 2 stroke and most people think they are unreliable in general.

However, this reliability is produced from Honda's Engineering, which means the engine must be left standard for maximum reliability. When these engines are tuned, reliability can reduce (but not always will be reduced). It depends on the ability of the tuner. The quality of injector oil used is also very important.

The problem in buying 2nd hand, you will never know 100% for sure what the condition of the engine components are. It may start OK, but you you don't know how much work the engine components have done. Crankshaft bearings can suffer from fatigue, at high km. Say over 20,000 km, but some cranks have been known to fail earlier and some cranks can still be OK at twice this. The crankshaft seals are an elastomer which will not last forever. If these seals work harden or perish, then you will need to split the crankcase and renew. Also, a damaged seal can suck air (and dirt) in which can wear out the big end and main bearings. You should also be prepared during the natural running of the bike to replace rings & pistons, which are the work-horse of the 2 stroke engine. But again if the engine is in standard trim, service intervals may be 10,000 km. But be prepared to replace the pistons & rings staightaway if buying a 2nd hand bike.

Other items which may need attention at some point are clutch plates (on the dry clutch model) and the water pump bearinbg / seal. This list is not exhaustive. If you are going to buy an NSR, you must be prepared to spend money on it, at some point. But when new parts are fitted, and the engine is standard, those parts will last for a good time.

I would look for a bike in your price range, with the lowest km possible, but be careful, new instruments may have been installed and the clock reading may not be true. Also try to find one which at least appears to be standard spec.

I would not advise buying a bike you cannot see. Its never failsafe, but at least view the bike, make sure everthing is straight, condition of bodywork etc. Then get the bike started and always from cold. Starting problems may means the crank seals have gone, or the piston rings are like razor blades.

If you do go to view some NSRs, you could do far worse than take some close-up photos and post them of this forum. There are many guys on here with vast experience and eyes for detail. You would at least get some honest and valuable feedback on the bike in question, before parting with your cash.

MC18 or 21 is a good choice. The only problem with an MC18 is that many new parts from Honda are, in general, not available. With the MC21, you can still buy most parts new from Honda, but not all! Being in Japan, you also have easy access to Jahoo Auctions, where there is always a vast supply of 2nd hand parts (for 18's & 21's) up for sale.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30