Why does my new, never been crashed, engine have a high freq. vibration even with a balanced prop?
Some engines are under counter-balanced; that is, the counter balance on the crankshaft does not have enough mass to completely balance the piston when the piston is at “top dead center” (TDC). Every time that the piston goes to “TDC” and crankshaft counter-balance is at the bottom of crankcase, then the piston is effectively heavier than the counter-balance. With this condition occurring thousands of times per minute, we have a high freq. vibration. What can you do about it? Try this. Take a prop and put it on your prop balancer, but don’t balance it. Just mark the heavy end of prop and mount the unbalanced prop so that the heavy end (marked) is 180 degrees opposite the piston when the piston is at “TDC”. In other words, when the piston is at its closest position to the glow plug (up), the heavy end of prop must be exactly opposite (down). This will help balance the heavy piston, and may solve your vibration problem. If it doesn’t, balance the prop and try something else because that
