Backstory. I have a ~1990 Snapper lawn tractor. Has 44" mower deck and 42" 2 stage snowblower attachments, 18hp horizontally opposed 2 cylinder Kohler engine and hydrostatic transmission. Works great. This winter, the throttle cable froze. In trying to free it up....I broke it. So I grabbed a ziptie, and held the throttle open about where it was at full throttle with the cable. Didn't take me long to realize it was revving higher, but I was enjoying the extra power. Last week, it was running strong, then there was a nasty clunk and it coasted to a stop. Last night I got far enough into the engine to identify what happened. 2023-01-28_02-35-58 by Numbchux, on Flickr Broken rod, chunk out of the piston skirt and cylinder wall, and it threw the big end of the rod up into the cam (gear driven pushrod flathead, so cam is right above the crank in the block) and broke it in half, too. I've thought about repowering it. But this tractor has a shaft drive off the back of the motor to the HST, and an electric PTO on the front for the mower deck/blower, it would require quite a bit of fu(&ery to adapt a different engine in there. I've looked long and hard at the Harbor Freight Predator 22hp V twin. While I think I could do it, it'd probably cost $1500 and a stupid amount of time. So now I'm on the hunt for a Kohler Magnum M18 or M20 horizontal shaft engine.... I can get the parts to rebuild it, but I'm hoping to find a complete motor (these were used in Cub Cadets, Simplicities, Toros, even Bobcat 440 skid steers, and more) that's serviceable.
I found this picture of it on the trailer right after bringing it home. 2023-01-31_11-22-56 by Numbchux, on Flickr
Kinda crazy it was designed to only run at part throttle and you were able to kill it just by opening the throttle more. I feel like in all of the lawn mowers I have worked on full throttle is just wide open.
I think the overrevving was the biggest and final coffin nail, but not the only. It does have over 1500 hours on it and is over 30 years old. The cooling fins were all packed with what looked like mud ( 30 years of moisture and dust...). The oil (which I had changed after mowing season last fall) was very black. Bought a pretty rough Craftsman yesterday with the same motor... 2023-02-06_02-10-27 by Numbchux, on Flickr
