In reply to Klayfish:
Are we still talking about the Chinese scooters?
Here's what I've found to be the biggest weaknesses.
First is gunked up carbs. The Jets are tiny, and it doesn't take much to plug one and cause a no-start. Any time it's in storage the carb drain screw needs to be opened. Running a bit of Marvel's mystery oil in the gas helps prevent corrosion in the carb. The factory fuel hoses are cheap junk. I always replace them the first chance that I get, and add an inline fuel filter. Some use a lot of vacuum hoses too, replace them at the same time as the fuel hoses.
They come with junky batteries and the charging system is just adaquite. When the battery is replaced, get a higher quality unit. Amazon has some pretty good AGM batteries for $35ish.
Another common cause of a no-start is tight valves. Chinese engines have soft valve seats, and the valves wear tight pretty fast, especially during break-in. Very often when you see a used low mileage scoot that won't start and the owner gave up on it, the valves are tight. The only thing that makes adjusting them hard is the body work around the engine.
A no spark no-start is usually a bad stator. The replacements are usually better quality than OEM, and are still pretty cheap. Special tools are required to replace a stator (flywheel puller), but the tools are cheap and readily available online. It's an easy job with the tools. Speaking of ignition, after market hi-po CDI units really wake them up, but it sounds like that's not what you're going for. If it didn't come with an NGK plug, put one in with the first service.
The plastics are brittle, handle them carefully when taking things apart.
Make sure to use good fitting Philips head screw drivers. The screws might actually be JIS, but anyway, a cheap ill fitting screw driver will strip the heads.
Change the motor oil as soon as you get it home, even if it's brand new. Automotive oil can be used, they don't have wet clutches. Also, change the oil in the rear gear drive, it's often forgotten.
Blue locktite is your friend.
Before long, you may find yourself wanting one. A tuned gy6 150 scooter will pull my big fat but around with no problem.