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This project started in 2005, then got shelved. It was going to be my counterpoint to the over weight, over tired, over priced, under braked choppers that were so popular at the time. I started out as a joke, but eventually I realized I had a lot of the parts I'd need to do it, so why not try to find a frame? I was hoping to find something that had been neglected (aka CHEAP) and put the word out on the bevelheads list. The first reply I got was from a buddy who had a frame that fit the bill perfectly (aka FREE).
A couple weeks later we met up at the AMA Vintage Motorcycle Days at Mid-Ohio and I picked up the remains of a Ducati 160 frame that some complete hack had sent him. The swingarm had been removed with a hacksaw, cutting into the pivot bosses in the process. The remains of the swingarm pivot was then removed from the frame with a sledge hammer. From what I can tell, the frame was laid down on the ground and beaten until the pivot was freed. And the subframe was bent. And the passenger peg mount was bent. And the pinch bolt bosses were crushed. And the serrated end of the footpeg mount was destroyed. They succeeded in removing the pivot but the frame was useless when they were done.
No sane person would restore this frame to stock. Maybe if it was a Vincent Black Lightning it'd be worth it, or some old boardtrack racer, but we're talking a square-styled Ducati 160 Monza Jr here. Out came the hacksaw and off came about 8 pounds of bent and battered tubing.
I've forgotten how I came up with the dimensions of the hardtail section. I probably I used a 250 narrowcase frame and swingarm I had, measured where I wanted everything to end up, and did the math. I bought the tubing from some online supplier, brought it in to work and manually bent it on a tubing bender. I didn't have a frame jig, so I drew a straight line on a tool stand I had and clamped the frame to it. Everything was centered and measurements were taken when adding things. It's not a race bike, it'll be fine.
I had decided to mimic the original frame tubes on the chain stays, coming out of the existing brackets with a 90 degree bend and running the tube straight to the new axle plate. I used the hole that the rear brake arm pivot went through as a locator for the new frame tubes. I had to enlarge the holes for the frame tunes to fit. First I turned up a bushing on the lathe so the bit for a hole saw would be centered, then tried to mount everything on the drill press. The test holes went fine with a 1" hole saw but when I went to do the frame things started to go wrong. It gouged the surface a little but I caught it before it was too bad. I got the hole through but it wasn't as clean as I would like. For the right side I went with a 15/16" hole saw and then opened it up with a reamer to fit the 1" tubing. I thought about doing this to begin with but decided the test holes were good enough... turns out it's a lot easier to drill through a flat plate than it is to drill through a bracket on a frame... oh well. Live and learn.
For the seat stays I decided to bolt them to the frame and weld them too after everything was in place. Belt and suspenders, I know, but I don't see a downside. If I don't like how the bolt head looks, I'll grind it down to match the profile of the tube, braze over it, then smooth it all down so when it's painted no one will be able to tell it's there. The tabs are there to mount the pivot for a sprung seat.
A couple weeks later we met up at the AMA Vintage Motorcycle Days at Mid-Ohio and I picked up the remains of a Ducati 160 frame that some complete hack had sent him. The swingarm had been removed with a hacksaw, cutting into the pivot bosses in the process. The remains of the swingarm pivot was then removed from the frame with a sledge hammer. From what I can tell, the frame was laid down on the ground and beaten until the pivot was freed. And the subframe was bent. And the passenger peg mount was bent. And the pinch bolt bosses were crushed. And the serrated end of the footpeg mount was destroyed. They succeeded in removing the pivot but the frame was useless when they were done.
No sane person would restore this frame to stock. Maybe if it was a Vincent Black Lightning it'd be worth it, or some old boardtrack racer, but we're talking a square-styled Ducati 160 Monza Jr here. Out came the hacksaw and off came about 8 pounds of bent and battered tubing.

I've forgotten how I came up with the dimensions of the hardtail section. I probably I used a 250 narrowcase frame and swingarm I had, measured where I wanted everything to end up, and did the math. I bought the tubing from some online supplier, brought it in to work and manually bent it on a tubing bender. I didn't have a frame jig, so I drew a straight line on a tool stand I had and clamped the frame to it. Everything was centered and measurements were taken when adding things. It's not a race bike, it'll be fine.
I had decided to mimic the original frame tubes on the chain stays, coming out of the existing brackets with a 90 degree bend and running the tube straight to the new axle plate. I used the hole that the rear brake arm pivot went through as a locator for the new frame tubes. I had to enlarge the holes for the frame tunes to fit. First I turned up a bushing on the lathe so the bit for a hole saw would be centered, then tried to mount everything on the drill press. The test holes went fine with a 1" hole saw but when I went to do the frame things started to go wrong. It gouged the surface a little but I caught it before it was too bad. I got the hole through but it wasn't as clean as I would like. For the right side I went with a 15/16" hole saw and then opened it up with a reamer to fit the 1" tubing. I thought about doing this to begin with but decided the test holes were good enough... turns out it's a lot easier to drill through a flat plate than it is to drill through a bracket on a frame... oh well. Live and learn.
For the seat stays I decided to bolt them to the frame and weld them too after everything was in place. Belt and suspenders, I know, but I don't see a downside. If I don't like how the bolt head looks, I'll grind it down to match the profile of the tube, braze over it, then smooth it all down so when it's painted no one will be able to tell it's there. The tabs are there to mount the pivot for a sprung seat.