Found this on a forum that I frequent quite often. Some people just don't understand how important SAFELY modifying a mower is, this guy found out the hard way:
LinkAt the job before that (small engine mechanic), we needed some competition for the golf cart we removed the governor from, so I had taken an old Sears lawn tractor, slapped a 20 HP V-Twin motor into, and replaced the 12" rear pulley with a nice 4.5" pulley. This thing was awesome. It had a separate clutch and brake pedal, so you should shift it like a car. First gear was a nice comfortable 8 MPH at half throttle. If you dropped the clutch in second you could ride out a wheelie for like 50 feet, and you would be going about 34 MPH which we confirmed at the radar sign that the police had conveniently left on Main St. This is a whole lot faster on a tractor with loose steering, wobbly wheels, and only a pivoting front suspension, so whenever you take a corner, the inside rear tire comes off of the ground. Finally I got the balls to put it into third gear. The motor bogged down a little, but this thing picked up speed incredibly fast. I went tearing down the gravel road to the electric company's facility behind our business. Judging by the 34 MPH in second, I would say it was going about 50 and this thing was fishtailing like crazy down the gravel road. Seeing as how I was going to reach the end of the road in about 5 seconds, I hit the clutch, and guess what... It wouldn't disengage, so, I'm just like f**k and held down the brake, which if you have ever seen a brake on a lawn tractor, it is like the size of a dime, and designed to bring the tractor to a nice slow stop from about 5 mph, and well it didn't do ****, so I tried putting the transmission into neutral, but the shift lever was stuck! Of course, at the end of the gravel road is a bit of a berm from where they plow the gravel. Miraculously I tried turning the tractor which caught the berm at an angle sending me flying off into the tall grass. At this point, I don't remember much of anything, but my boss and another employee watched the the tractor go tumbling end over end, hit the septic berm, which caused it to fly about 15 feet into the air, and smash into a pile of railroad ties.
Aside from a sprained ankle, jammed finger, and a mild concussion (The helmet was kind of an after thought), I was OK. The tractor wasn't. The impact tore the front axle off of the tractor, and ripped both spindles out of the front axles, and the frame was bent downwards at about a 15 deg angle on the right side. The battery went flying about 40 feet past the pile of railroad ties.
We determined that the cause of the failure was where I ran the belt. along side of the shift lever. First and second are on the left, while third and reverse are on the right. Originally the shift lever was in the middle of the two sections of belt, while after I was done modifying it, both sections of the belt ran on the right side which got caught on the bend in the shift rod where it was routed through the frame.
Cliff notes: Crashed a lawn mower going about 50 MPH with mild injuries.
