I find a vacuum/pressure checker handy for working on two strokes. You can buy a hand vacuum pump pretty cheap from harbor freight. Then you make a plate to seal off the exhaust and the intake right where the carb mounts. Use rubber gaskets to seal the plates, and in one of them put a valve such as used on auto tires. With all in place, pressurize the engine to no more than 5 psi. It should hold the pressure, and you can chase down any leaks with soapy water. Then, remove the valve core from the valve, hook up a hose, and pump it down to a vacuum. It should hold the vacuum. If it passes these tests, you know the engine is well sealed and your problem lies elsewhere.
(Jim, add to "sticky??)
AV8TOR