Mike, I have never had a moisture problem with fuel and I only buy fuel in cans so it doesn't go bad even with long storage so I have never had a fuel problem. But {you like how I got that but in there} I have had a problem after what I will call hard landings, like when I have flown through a tree. Bent needle valves being just one. After a hard landing I have also had to use a different size prop than what I had on before and the engine may not like the new prop well enough to idle like it used to so a bit of a tune may be called for. Just going from an APC to a wood prop of the same size can do it. After a hard landing I have even discovered a bent push rod tube rubbing the push rod and putting it at a strange angle. If leaning out the low end made the engine run a lot better but not quite right then perhaps giving it a bit more twist would make it run correctly. Maybe it would like to have the valves checked and/or adjusted at this point?? Just a lot of little things can effect an engine after a hard landing. I had one OS .70 that gave me fits after I parked it in a tree. OS service wanted the price of a new engine to repair it, they sent me a list of everything they found wrong with the engine. I had them send it back to me. I got a box of parts. I took the parts to a local service and had them inspected, they didn't find any of the problems OS did? That's when I started doing my own service. I put the engine back together and it still wasn't running correctly. I installed a new needel valve assembly like I asked OS to check and the engine ran perfectly for several years. It can be something that simple after a hard landing.