At the start of 2006, I was looking for a new project; I try to build a vehicle every year. I found out that a 1/8-mile drag strip was going to open nearby for the summer season. I decided to build something to race. I had wanted to build a funny car for the street, but I don't have a trailer and hate towing vehicles, so I decided to build a drag bike, which I could carry in my hot rod pickup. What should I use for a motor, I had built many drag bike frames for 500 and 750 Honda, but that did not interest me. I was visiting a friend, legendary VW builder and driver Bob Hoffeld, and the answer came to me. On the floor of his shop was an IRS VW transaxle. I noticed the flanges on either side of the differential were about the right width to drive a motorcycle rear wheel. I asked about how I could reverse rotation of the rear end to put the motor ahead of the tranny, and Bob told me if I used a 1969-1972 VW transaxle, you could remove and reverse the ring gear to the opposite side. Now I knew what to do.
I got a dummy motor and transaxle to start the frame. I also got a rule book to check on current requirements. I found out that drag bikes were not allowed to have foot controls. Well, I could easily use hand brakes for front and rear, and standard twist throttle, but using a hand operated clutch lever for an automotive clutch probably would not work, and how could I shift. Pro Stock drag bikes use air shifters, but that cost too much for my backyard racer. Weight was also a concern, and the motor was to far forward in to clear the shifting mechanism. I decided to fix all those problems by building a glide clutch, like the top fuelers use. I would remove all the shifting mechanisms, which allowed me to move the motor 7" farther back; I removed all the internal gears in the tranny, locking it permanently in high gear. This saved considerable weight. Now for the glide clutch...
I am on the pit crew for a AA Fuel Altered, so I am familiar with glide clutches and how they work, but I was not sure how to build one. The bell housing on the VW motor was not very deep, so one disk was all I could use. I got out my machinery handbook and found formulas for centrifugal clutches, and contacted a clutch disk manufacturer for advice. We decided to use an aggressive disk, which would last a long time with the loads I had. I drew up a design and contacted Randy at East West Clutches to check my design. Now confident, I built the clutch.
I needed to stop rotation of the differential, so I went to order a spool for the VW differential, too much money. I welded up the spider gears, which has worked great, and added a sprocket to the flange that originally held the half shaft. Now all the motor dimensions were complete, so I started the frame.
One inch .095 wall tube was used for the frame rails and 1 1/2 by 3 inch rectangular tube for the top rail, which doubled as the gas tank. A neck was machined and I set the rake at 40 degrees. I fabricated the frame, got a Yamaha 650 dirt bike front end at a junkyard, lightened and shortened it and mounted a high-speed tire. I bought an eight-inch wide drag slick, mounted on an automotive wheel, built a hub and axle to hold that wheel and added a motorcycle style disk brake. Custom hand operated master cylinders were mounted to the handlebars. I added a steering dampener to add stability at top speeds.
Now for wiring...I did not want to carry a battery for weight purposes, so I got a magneto and mounted the VW starter that used a separate start cart with a battery. I started with a 1641 cc motor, relatively stock, to check things out. Added dual carbs and oil overflow tank. I decided not to drive the bike myself, as I am large and have too much wind resistance. I asked retired top fuel Harley rider "45 Bob" Thomas to drive the bike.