My advice to buy a brand new bike and used bike are:
Before purchasing a new bike, one thing always keep in mind that there must be kick option.
Its not necessory that minimum or higher cc.
Before driving, start your bike first through kick only, after one minute while oil flow in engine ran smoothly.then go for ride.
Running Speed of your new bike or after service of your used bike, it should be less than 40.
Try to rest you bike after 20 kms.
In case of raining season, try to clear mud from chain and try chain lubricant.
Try to maintain full air, on back tyre should be 35 and for front should be 25.
7 always mmaintain your speed for one week after service.
Always check engine oil before start a bike.
Please do not pull cluth unnecessorily.