Too Big

[SpudsPaP]

Hi Does anyone think a 150 cm or a150 cm motor is too big for a 1970s mini bike ???

[whome]

Hi Does anyone think a 150 cm or a150 cm motor is too big for a 1970s mini bike ???

No, Harbor Freight sells a mini-bike with a 212 cm, 6.5 hp engine. bolt on racing parts, identical to Honda, the engine can be brought up tp 12 hp, or so'. The only problem is the engine is fitted with a lock-in centrifugal clutch, making a gentle start nearly impossible. the engine idles around 1900 rpm and the clutch engages slightly above that. The cam action between the shoes and the driver causes the clutch tp lock in instantly so the bike starts with a severe jerk and is doing about 19 mph instantly. With the standard gearingthe top speed is less than 25MPH, WITH RIDING DOUBLE TREE CLIMBING TORQUE. If you upgrade the drive to the variable speed drive, take-off is softer, and top speed is around 47 mph. I built my first mini-bike in 1943, and several more until our son was big enough to ride a street-legal dirt bike. The Schwin frame had lots of room for the engine and I used 4 step pullies with belt drive and foot actuated belt shifter, The belt rightening clutch idler was held engaged by foot pressure on a pedal. Rear drum brake was typicall, sometimes used a Morrow? bicycle brake. The Schwin multi disk coaster/brake had so much internal friction while running under At 84, some of the details I have forgoton, though I did fit every bike with an earles forc/front suspensiln, and a well sprung seat.ower that it would sieze up and lock the wheel. It could npt be unlocked, so you had to lift the back wheel off the ground and walk home.

Second big problem is the tires rarely hold air for log, sray them with soapy water and watch fine bubbles develop in the sidewalls. I ordered a new front tire for my grand son's bike and the sidewalls leaked like a sieve, so I put a tube in it.