I have a M18 Kohler Magnum (Spec# 24608 ) on a Grasshopper 718K. The mower sat for a while. Before it sat up it worked pretty good. When I went to see how it would run - it sputtered and the governor would hunt and would backfire. I performed a quick cleaning on the carb ( it was gummed up) and I replaced the air filter, spark plugs, and the gas and gas filter, I even replaced the old line with new line. It runs much better now and hardly hunts anymore but I am not getting any power from the mower when I engage the blades or try to move. If I do both the engine sounds like it will die. O.K. I now re-cleaned the carb (fully cleaned -- 3 day acetone dip and used a carb kit), I cleaned the carbon off of the heads, valves and pistons. I lapped the valves/seats with compound and a hand lapping tool , they are now all with in lash specs, Replaced the intake valve seals (none on exhaust), cleaned the intake manifold, I also replaced the breather filter and breather/valve cover with that little 'flapper valve'. I bought a gasket kit and replaced all of the gaskets that I took off. I torqued down everything to specs. Adjusted the carb to initial specs and reposed the oil and filter to correct level. It will now start up great and it no longer backfires or governor hunts. I am still having power loss engaging the blades or trying to move. I even took the deck off and just 'rode the mower' and the power was cut by 1/4 the power or more. (it would seem - no way to know exact power loss #s). This is better than before but the power loss problem is the same. I also want to state that before one cylinder would get very hot and after the tear-down it still gets very hot. (example: I can barely touch the exhaust bolt on cylinder side #2 [left side facing flywheel] -- on Cylinder # 1 I can touch it for a few seconds). I have no idea if it is normal for one cylinder to be that much hotter that the other. I did a compression test and I get around 95 psi for both cylinders (one 95/96 the other was 94/93). I think this is low but I did one a couple of years ago (right before Hurricane Katrina Aug '05)and it was only slightly higher and ran strong. I am thinking about getting a leak down tester at Harbor Freight tools and see what that tells me but I am at a loss here. In-line spark tester shows spark (I don't know how to test the quality of the spark) oh also since this is a twin and I read some post about removing the plug to see if it was running on one cylinder. It I remove either plug the engine will die. The post were on newer engines so I do not know if it pertained to the Kohler magnum twins or not. One last thing, the reason it sat was because Hurricane Katrina tore my shed apart and a limb fell across on top of the air cleaner. It bent the air cleaner assembly and that was replaced and the intake manifold 'appears' to be good and flat when I cleaned it. It it was a hail line crack that I could not see... would it cause me problems? Sorry for the LONG post but I know you guy like to know the facts and figures so you can post a more accurate response. Recap: 1. One cylinder/side is much hotter than the other. Normal? 2. Starts good and runs until you put a load on it. Thank for any help that you can offer. I can get what ever information that you need (unless I don't know how).