I call it the Ultimate Chopper. I designed it after the chopper ridden by Peter Fonda in the movie Easy Rider. The bicycle base is a Schwinn from the mid-60s, stretched 15". The pedal crank was heated and twisted into a U shape and reinstalled in the frame bottom hanger to form a set of footrests. I used the standard pedals for effect. I also installed the chain ring to maintain the bicycle look. The frame neck was raked 1 inch and a Schwinn spring fork fitted with a Puch moped front brake, as well as a caliper brake. It's easy to add a motor and make them go but it's something else to make them stop efficiently. The rear wheel is a 17" moped rim with no rear brakes. The tires are 24 x 1.75 on the front and 17 x 2¼ moped on the rear. Both wheels are fitted with heavy 120-gauge spokes. Regular 80-gauge bike spokes will break easily and can be unsafe.
The most eye-catching part of this motor bike is the Stars and Stripes paint on the tank. The tank, of course, is not the fuel tank. The tank is a Schwinn horn tank, which has been widened to create eye appeal.
I have built motorbikes using the Tecumseh 3 horse and the Briggs and Stratton 3.5 horse, which have been good riding and good performing bikes. However, the Ultimate Chopper is fitted with the 5.5 AP Briggs and Stratton OHV engine, Centrifugal clutch with 3 ½-inch drive pulley sending a V belt around a 7" reduction pulley mounted on a jack shaft next to a 6" pulley, which drives the final 16" pulley attached to the rear wheel.
This bike weighs about 100 lbs. and I weigh 210 lbs. and this 5.5 hp engine with the 7" to 6" to 16" ratio pulls off the line at the green light as fast as the average automobile driver accelerates. Between 35 - 38 mph. The traffic goes off and leaves you only to wait for you at the next light and start all over again. All the time giving you somewhere near 100mpg. I tried various size pulleys and this combination works best, you get good off-the-line acceleration, good mid-range response and the best top speed for bicycle type tires and brakes. Bicycle and moped tires will start to come apart at sustained speeds over 40 mph. High speeds on a bicycle frame require the frame to be raked 1 inch; a straight up fork will result in pronounced transmission of road surface shock. A spring fork is desirable but does not take the place of a raked frame.
Don't just motorize it; build it with Style and Grace.
