I just cleaned and mounted my prop hub on my Echo 21cc motor , when I rotated the prop back and forth by hand [not in a compression stroke], it makes a very light metallic ticking sound, the motor only had about 2 gallons of fuel /oil mix ran through it while trimming the lawn, so my question is if you should try this rocking motion with one of your engines do you hear a slight metallic sound? OH and one more question, do you put any locktite on the flywheel threads so the aluminum prop hub wont come off?

Ron, I know the sound you hear, I've heard it too. I think it might be the lower rod needle bearings nomal play when the engine is cool. Maybe something else but all I know is mine goes away at operating temp. Locktite is a good idea in any case but if you remove it often it becomes a chore. I havent every played with an echo, so as long as its not left handed threads you can get by without locktite. The power pulse from the engine help keep the hub tight on a shaft with normal right hand threads. I havent put locktite on any of my hubs and havent head a mishap yet. If your engine is left hand threaded my I suggest J.B. Weld and a monkey wrench...LOL I've heard some bad stories on here bout that. Hope this helps. Mike