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My motorbike called "Frankenstein"

By Mike Chiavetta

     I am a member of the Donut Derelicts car club from Huntington Beach and have attended the weekly early Saturday morning gathering of Hot Rods for more than 20 years. Lately, several gearheads have been driving their newly made motorized bicycles to the donut shop. Not just the average Schwinn Whizzer's or Chinese motorbike kits but hopped up aluminum Briggs and Stratton lawnmower powered motorbikes with significant 6hp and style.
     I decided I needed to make one for myself and found a trashed mountain bike that would be good material for a start. I admire 1920's board track motorbikes, so I did a web search and discovered that the Henderson Bicycle Company also made motorcycles and often raced them. Now I knew what I wanted my project motorbike to resemble, a Henderson board track motorbike.

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     I cut my frame in many places and by using a few bends from a broken steel lawn chair, welded up a lengthened frame that would saddle my Kohler engine. I was told that most muffler shops will make you the few bends you might need. I took my bent mountain bike handlebars, made a few cuts, lowered the weight of my car on the bars and flattened the whole shape. Once the cuts were welded and mounted upside down, the modified handlebars became very authentic looking.
        I had been saving my garage sale found cast iron Kohler industrial engine for years and now I finally had a use for it. For simplicity sake I used a centrifugal clutch (, and lawnmower chained the power to a half shaft. From the half shaft, I bicycle chained the power to the rear wheel sprocket. I used an extra bicycle crank bearing assembly for my half shaft but I needed to weld a key slotted shaft on the crank shaft once the pedal arms were removed. A machinist friend made a shaft and used a lathe as an alignment tool to accurately line everything up before welding.
   My mountain bike rear wheel rim had to be replaced because it was damaged beyond repair. I used a good beach cruiser style rear wheel as a replacement. Now I had a coaster brake and I could also use the standard mountain bike brakes (front and rear) for stopping power. The large diameter mountain bike crank sprocket was sandwiched between a 1/8" thick rubber disk and the spokes of the new rear wheel.

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     For my exhaust header, I shaped a centerline from an old brake line and had a  local company that bends railings for boats make it from ¾ " tubing. They suggested using stainless steel tubing, but I wanted mild steel for an authentic rusty appearance.
     I used an old elliptical 30's Chevy brake light for a head light and had a new lens cut from fluted clear glass at a local stained glass shop. I wired Mini Maglite 2-Cell AA Xenon replacement bulbs ($3.25 a pair) into the light housing reflectors because of their bright intensity and size.
     Because I am versed in composite construction (, I made many parts from scrap carbon fiber cloth we had laying around our shop. Less expensive Fiberglas cloth would have worked well too. I made a fender, seat pan (covered in leather from an old brief case), chain guard, brake lights, switch /AA battery box, a fake oil pan and a vintage license plate.

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     I learned that I could make anything by shaping my parts from surfboard foam, cover the surface with common masking tape, coat the tape with car wax and do a 4-layer lay-up over the tape. Once cured, the foam and tape can be removed and the part can be sanded and painted.

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     A legal license plate (the white one) and registration is easily obtained using a downloaded form (REG 230) from the Department of Motor Vehicles. Mail a one time fee of $19 and a completed application form and you are licensed and legal to ride. As long as your motorbike can be pedaled like a bicycle and you promise it won't go faster than 30 mph it will be legally recognized as a MOPED/Motorized Bicycle by the authorities.
     All in all, it was a very inexpensive/creative fun project (about $150). I used plenty of old bicycle and lawnmower parts with lots of barn find patina thrown in. My son helped me with the welding and I made no attempt to refine the scars thus my motorbikes nickname is "Frankenstein". Best of all, it doesn't take much space to store and it's a blast to putt down the road on a whim when the weather is fine.
Go for it, you won't be disappointed.

Mike Chiavetta
Huntington Beach, Ca.

(click on photo to enlarge)



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