I am building this bike for the Oregon Gambler 100 mini bike offroad endurance race in May. The race is 18 5.6 laps on single track trails with strait aways, whoops section, and the "devil's butthole" which I'm guessing is mud. There is a 3hp and under class, and an over 3hp class. Their definition of a mini bike is a two wheeled machine powered by an industrial style engine with a centrifugal clutch. I'm entering the 3hp and under class because I feel like it won't be as competitive...... and I aim to win, ha.
The plan is a scrach built single sided frame and forks, 79cc HF Predator, 2 speed jackshaft (they didn't say anything about multiple clutches), and 22x10-8 Kenda Snow Mad tires on widened wheels. Yes, I know the tires are huge for a 3hp engine, which is why I'm running a 17.5 low gear and a 10.7 high. According to my calculations, with a 1500 rpm spring in the jackshaft clutch, second gear should kick in around 3300 rpm. Engine mods will be intake, exhaust, gov removal, and rejetting. If the engine will rev to 5000 rpm after the mods the top speed should be about 30.5 mph in high gear. This bike will not have suspension for simplicity and light weight, but will have a nice hydraulic mountain bike shock under the seat.
The plan is a scrach built single sided frame and forks, 79cc HF Predator, 2 speed jackshaft (they didn't say anything about multiple clutches), and 22x10-8 Kenda Snow Mad tires on widened wheels. Yes, I know the tires are huge for a 3hp engine, which is why I'm running a 17.5 low gear and a 10.7 high. According to my calculations, with a 1500 rpm spring in the jackshaft clutch, second gear should kick in around 3300 rpm. Engine mods will be intake, exhaust, gov removal, and rejetting. If the engine will rev to 5000 rpm after the mods the top speed should be about 30.5 mph in high gear. This bike will not have suspension for simplicity and light weight, but will have a nice hydraulic mountain bike shock under the seat.
