Trimmer was running horrible, killing at full throttle, hard to start, etc. Tried seafoam, seemed like the problem was solved initially, but once the seafoam was burned off, the trimmer ran bad again. I had to dismantle my redmax trimmer in order to clean the cylinder head, piston and internal engine parts, due to running too rich an oil mixture (40:1 instead of 50:1). These parts were black and had thick carbon buildup. I cleaned them with a dremel tool wire brush and seafoam on a rag. This got everything very clean. Now I can't get the piston back into the cylinder. I'm not a mechanic, but I know that you have to squeeze the rings to get the head back over the piston. Everything seems to fit too tight and I'm afraid to damage something if I keep trying. I can't get the piston past the second ring, is there an easier way to do this?? Any help would be appreciated... thanks!