I know this may sound foolish but after I started flying mine this season I just started it up and flew it thinking all was well as i had 20 hours on the plane last season. It started to sound like the muffler was falling off after the 3rd flight and when i looked it over all seamed ok so i went up a 4th time and did a high speed pass and it gor louder when i landed all 4 prop bolts where busted the spinner was all that was holding the prop. Seems the wood dried up and shrunk over the winter on my prop and things got loose.