A friend of mine had a job as a runner at mid-ohio dirt-bike race track as a teenager, & he rode his VERY tired mini-bike to run errands. One day, he ran out of gas near a pit crew, and they offered nitromethane to get him back.
As he put it, that tired old B&S minibike turned into a rip-roarin', hill-climbin', dirt-throwin', back-down-from-nothing SOB for about a minute. Then, the engine disassembled itself.