Minibike Madness
One of the things I distinctly remember from the Rod Runs of my youth were luggage trailers and pop-up campers behind street rods. Something else that seemed ubiquitous were minibikes. Everybody had one. A lot of times they were packed on the luggage trailer, as ours was, so it could partake in the fun as well. While an awful lot of fun, these little scooters served a practical purpose in their time as well. They saved a fair amount of hoofing it to the outhouse from wherever you had your camp setup.
Recently there has been a renaissance of the Rod Run format of years gone by. Events that span several days, include games, contests and activities for participants of all ages, car games and competitions, live music, camping and a festival atmosphere. You’ll bring your lawn chair to these events, but you might not use it all day. Along with this shift in format, also came the minibikes. Whether used for leisure putting, drag racing or dirt flat-track competition, these mini menaces are back in force.
The first event we attended that included events for mini-bikes was the Rust Revival show in Wayland Missouri. What started as a few guys with minis drag racing on a closed down Village street, has ballooned into a full-fledged bracketed race with classes and tech inspection. How cool is that?
Soon, other shows in our area began to embrace this key part of our adolescence as well and started hosting events that included minibike races. One of the best organized and executed was the Scene of the Crash show in Sioux City, IA. This was the event that convinced me that we needed to build one.
With the mold cast, I started out in search of a Sensation Manufacturing Mike-Bike chassis with which to begin. The bike my Dad had when I was a kid was this make and they were produced in Omaha in the late fifties and sixties. My search ended when a friend I’d tapped to locate one called and informed me he’d purchased one for me. It took a whopping 3 days to secure the basis for our project.
After about a week of gathering parts from various sources, we were ready to begin terrorizing the neighborhood. I located the old five spoke mags & tires I always wanted as a kid, brand new on E-bay. Power comes from an off-the-shelf Predator 212 engine from Harbor Freight. If you watch the sales and coupons, this engine can be had for a paltry $99. If you miss the boat and pay full price, it’s still only going to set you back $129.
I also was able to source some quite effective hop-up parts for the 212 Predator engine via E-Bay. Taking the original horizontal shaft 6HP mill up to a respectable 8-9HP. This consisted of a free-flowing straight head-pipe, a jet kit and open element air filter. A slight amount of studying the throttle apparatus also made it possible to bypass the factory equipped governor. (This will void your warranty)
The centrifugal clutch and #35 roller chain come from our local farm store. I happened to have some grips and a throttle banked away from past cycle projects.
With all the bits in place, my daughter Kaityn and I set to work at 7 am one Saturday morning. The assembly was very straightforward. While the chassis was set up to accept a 3-3.5HP Briggs & Stratton engine, the Predator engine accommodates the exact same footprint and bolt pattern. The most time-consuming part of the process was building spacers for the rear wheel axle to properly space the sprocket.
Our first test blast was successful and we baselined the performance with a GPS. In completely stock condition the combination went 34MPH top end with my daughter on it. So naturally, we ripped it back apart to make it go faster. We also wanted to spruce up the look a bit too. While the engine tins and gas tank were drying with their fresh coat of ivory paint. We went to work on the performance.
After some slight disassembly and fitting of a new straight exhaust pipe, velocity stack and re-jetting, we were ready to take another run at the record. Kaitlyn’s second attempt netted a trap speed of 46 mph.
We decided that was fast and quick enough so we turned our attention to the overall look of the bike. It had some hastily applied black spray paint. It turned out that it was easily removed with some lacquer thinner on a rag. As we found, the teal paint underneath looked pretty cool and had a nice patina. It also matched the Norwell poster hanging on the wall. Which was good enough for us.
The crowning touch was the upholstery that my buddy Larry Cain did for the plywood seat blank I cut. The cover was made with the same press-pleat vinyl I used years ago in my green ’54 Chevy, Larry made quick work of the seat. Naturally, we also had to give it a little extra accent with some vintage and contemporary performance decals.
