This engine is hard to start by hand. I used the electric starter on it then it will start no problem. My engine vibrates a lot. Every few minutes of running, all 5 exhaust pipes come loose. I used red, purple, blue locktite but nothing worked. The propeller is perfectly balanced. The last time test ran the engine for a few minutes, the exhaust pipes didn't come off so I thought I finally found the right locktite. How wrong I was, after 3 eight minutes flights, all 5 exhaust pipes came loose and broke. I sent the engine back to the seller for repair. It been sitting there for almost 3 months now.