Check it for air leaks. pressurize the whole engine to about 3 PSI through the intake port or spark plug hole and spray the whole thing down with Windex or Mr. Bubbles.
3PSI max or you risk popping the crankshaft seals out. Easy enough to reinstall, but why make more work for yourself.
Here's a video of it being done:
Leak Down Test For 2-Stroke Engines.avi - YouTube
The guy in the video says 9 PSI, but I would not recommend going above 5 with these Chinese engines.