UPDATE: Mike wrote the following over on the Yamaha Enduro message board about the build. Hope you guys don’t mind me adding it here. He’s responding to Ctune1 on that board:
Hi Mark-The inspiration for this bike came from seeing the Ducati Hypermotard at the Cycleworld show. Sabrina thought it was cool and suggested we build a “RetroRetard” of some sort. She didn’t have a bike or know how to ride but said she would and started looking for a bike. She soon found a CT1 on Craigslist and we went and picked it up in Hollywood for less than $100. It was mostly all there but we found out the motor was shot. I was working at WCC and we had a yamachopper which had been making the rounds and nobody ever got it running or rolling, so as it was a really awful mess I took the motor from it. We test fired it in the garage and nearly set the place on fire as I just had rigged the ignition and sprayed choke cleaner in the intakes while cranking it over. There were no carbs even so it just sort of roared and died in a ball of flame which eventually went out.
Inspired, we sat the engine on the ground and started hacking into the CT1 frame. The frame mods consisted of completely removing the down and under tubes originally in place for the 175. Then I ground and smoothed all the nubs and uglies off the frame top tube. Then I draped the frame over the engine which we had set on blocks on the ground. From there I could see it was possible! I drilled the rear down tube for horizontal “through” tubes which I tig welded in. I made alloy plates using cardboard templates to get the shape right. The same thing was done with the top head mount. The head had to be narrowed in the milling machine in the top mount area which normally is 3 inches wide or so. I milled it down to the same width as the top tube and made alloy plates to hold the head.
This had to be done to fit inside the tunnel of the fuel tank. Next I bent up some 4130 tube and made the engine cradle. Again I drilled through holes for the front mounts and welded in footpeg mounting bungs. After that the brake pedal was modified to fit. I made a battery box and mounts for coils and starter solenoid all under the seat.
The tank also had to have the seam on the bottom ground and smoothed to clear the head nuts. It’s pretty tight but it all fits.
The pipes I made also from mild steel bends. The mufflers are my own design with a chambered “flowmaster” style interior. The outer muffler plates I dimpled in the hydraulic press with some tooling I made before welding the muffler bodies together. The heatshield decoration is made from ¼ “steel rod, bent, welded, chromed.
Rear wheel is xs650, front is original but is soon to be replaced with a twin leading shoe unit from an r5.
There were a few other bits and pieces it took to get it all working but it’s a really fun bike to ride. It fits Sabrina perfectly, she learned to ride on it, went to a riders school and passed her test. She rides it a few times a week and it’s been really great fun. She loves the character and mechanical nature of the beast. It has way more character than modern plastic bikes all covered up, and starts easily and sounds great.
Next up on the list is a 350 sprint I have had sitting around for a year or so.
Best wishes to all, Mike
Mike Cook sent in thses pics of this really creative build.