Howdy. Dad just called and his 05 ranger 500 won't fire. Compression is 0. getting blowback through the intake. Seems to me that either means stuck valve, timing problem or valves finally need adjusting. Looking for specs on compression and on valve clearance. I am not sure how the rockers work on these engines. Are they overhead like the old hondas with a chain drive or are these push rods off a cam shaft. ANy suggestions would be greatly appreciated since he uses it on the farm a lot and at 81 he needs something that works.