I had been thinking about this idea for some time. In the zillions of phone calls, emails, and discussions I have had over the years with Ducati experts, mechanics, and racers, I've learned that with most of the post 90 machines, the bottom ends of SS machines, Monsters, and SBK bikes were quite similar -- especially in how the engine mounts to the trellis frame. All of the championship-winning Ducatis, as well as the bikes you can buy from the showroom, are mounted by a grand total of 2 engine bolts to the steel frame. The swingarm pivots on the rear of the case. That's it. Even better, the location of the mounting points for everthing from a lowly 400 monster to a 999R are in exactly the same place. Theoretically, most of the hard work is done if you wanted to swap an engine from one bike into the frame of another. Switching an aircooled engine (with all its simplicity) into a SBK frame should be a piece of cake. From my experience, it was.
The first step was to find a suitable frame. Since I already had a modified tank to work with the SS fuel pump (see below), a 748/916 style frame would be the easiest. I was under no misconception about Ducati's claim that SBK frames were chromoly. THEY ARE NOT! All of the frames I have ever seen and cut apart -- SS, monster, and SBK "S" frames, are seamed steel -- likely 1040 or something. This is fairly cheap ERW steel, with the joints mig-welded. A sound design for sure, but engineered to be assembled quickly and easily. That being said, I had high hopes that the 748R frame I was able to buy from ebay would be different. It was and it wasn't.
When I got my hands on the frame, a 2002 model, some differences were apparent. The bent tubes aft of the steering head and fore of the vertical cylinder had more of a "bow" to them -- this proved that it was an R frame to accomodate the larger R airbox. That being said, I still had to trim a section of these tubes to clear the intake manifold. Sure enough, while the wall thickness was thinner for this frame, the telltake seam on the inside of the tube proved that it was not aircraft-spec 4130.
However, like all S and R framed superbikes, it did come with an adjustable steering head -- cool! However, to be cautious, I set it at the slower geometry for now... At the back of the frame I designed a fabricated a truss for the cantilever rear shock. Other guys have incorporated the SBK rear swingarm, but this involved a lot of cutting to the engine case, and the SS swingarm weighs a ton anyway -- I know, I've held one in my hands. The aluminum swingarm is lighter and of course, I had one already.
I saw fairly early on that an OEM, Ohlins, or Penske rear shock with the integrated remote resevoir was going to be a headache to fit... so I found a Paoli adjustable shock, with a real remote resevior for a great price on ebay. In reality, even though the ad said it was for a Ducati, I'm thinking it came off of a DB2 or DB4 Bimota. The overall length of this shock is actually shorter than a pre-99 OEM Showa shock, so it can't have been for a Ducati... they steer too slow as it is... with a lower rear end, it would almost be unmanageable. This actually suited my needs perfectly, as the truss would extent almost an inch shorter than usual, making the whole assembly stronger. The truss was made with a combination of 1015 steel tubing and 4130 steel, oxy-welded together by yours truly. Some significant trimming needed to be done to other parts of the frame to accomodate the swingarm pivot and the routing of the shock, but nothing was too difficult.
The last step was to either hog out the engine cases to accept 12mm engine bolts, or sleeve the frame to use the 10mm bolts I already had on hand. I chose to modify the frame beacuse I could do it, and I already had Nichols/Cyclecat engine bolts on hand in 10mm sizes.. purchasing the equivalent in 12mm would mean another $250. After many test-fits, I got the frame sandblasted and primered.
