There are several things we should be careful about when we're going to buy a used motorbike.
1. Hire a reliable bike expert to check the bike condition.
2. Look if the bike parts have been replaced. Usually when one has to replace a bike part say, R1, he won't go for the genuine yamaha motorcycle parts
, as it is way expensive than the ones that can be easily found in the market.
3. Check for all the papers. The engine number, RC papers and ownership papers or if its on hire, the authority papers, etc. etc.
4. Ask for some time to check out the ride. You might not be able to find mistakes on the spot so while signing the papers making such an agreement would be wise.