I lost a really nice, half-year-old Toro lawnmower to a mouse once. The pesky thing built a nest under the engine cowling over the winter. The cowling was solid, so I didn't see anything amiss. After 15 minutes of mowing, the engine started to rev really high. I couldn't shut it off. Then it just blew up. The fire started by the nest overheated the cylinder and
ka-pow, the damn thing blew a quarter-sized chuck of steel out of the cylinder wall. I ran in the house and grabbed a fire extinguisher and put out the fire. My neighbor was in stitches. He kept saying, "Only you, man, only you."
I finally cleaned the thing up, put it back together, and brought it back to Home Depot. I played Mickey-the-Dunce with the sales clerk there and told him the damn thing just won't start. He tries it and sees there's no compression, so he shrugs his shoulders and tells me to go grab a new model and he'd exchange it. Gotta like Home Depot.
The new model was indentical except it had several holes in the cowling, so I'd geuss I wasn't the only one with that problem.