I just replaced my crankshaft on my engine because it got bent somehow, I never crashed it or have ever broken a prop.??? Anyhow I took it all apart and found it never had a gasket installed from the factory between the head and the crankcase.[X(] I then found that the original crank was poorly machined compared to the new one. The new one has some kind of black coating along the shaft and the counter weight. You can see a lip of unmachined metal on the old crank on the left.This engine runs great but you need to almost take them apart and go over them before installing. NO locktight any where, as mentioned previously.