had one for a long time, 5hp briggs
as I got older and better, I quit riding it and continued riding a YZ125, traded that for a YZ250. I can't ride a 250, just too much power for my skillset. Found a CR125 and traded the 250 for it. I worked at a dealer at the time. During my time there I came across a lot of stuff. One afternoon a guy dropped off a Yamaha DT50, street trail, 50cc liquid cooled. High strung little thing but super easy to ride. I got it going, called him and guy never showed up to pick it up. About a year later the boss said get that thing out of here, make it disappear. I paid the bill ($90 as I recall) and took ownership of it. Gave it to my brother. He rode that thing EVERYWHERE. Mud holes, dirt, through the forest, across town, highway, streets, didn't matter he rode it. I think he put something like 12,000 miles on it. Keep in mind, it made NO power until 8500 RPM and it was like turning a light switch on. From 8500 to 13,000 it ran ok. Top speed right around 60 turning 15,000 RPM. He wore it out, I did a top end overhaul on it and got it going again. Then he wore it out again and I let him start riding my CR125. Boy he liked that. I picked up a used 4 stroke and rode it, we rode together a lot. The whole time, from my age 13 through 19 the old mini bike just sat there. At 15 I bought an old Ford Maverick and fixed it up, eventually made a drag car out of it. Brother was still young so we looked at getting him a Junior dragster (half scale rail car). Those are powered by a 5hp briggs based engine. Some of them make 45hp or more. I was shopping for jr dragsters and a guy I knew had an engine but no chassis, dirt cheap. I bought the engine and figured I'd find a chassis. Never did, he got old enough to drive dad's Ford Fairmont drag car and that was that. I took the old dragster motor and bolted it to the minibike for giggles. It was a 3.5" bore 3.5" stroke, big cam, ran on methanol. Thing hit hard. WAYYYY too much power and speed for the minibike. Wheelies were easy but so was crashing. Yeah it was fun for a whole 5 minutes. Took it to the race track to try to run it down the drag strip and they wouldn't let me, so I half-heartedly hung a for sale sign on it in the pit area and some guy offered me a sizeable amount for it which I obviously and un--reluctantly accepted.