A few things came together this weekend -- a pleasant Saturday to work, and parts and machining all arriving in time for me to play with.
First up, the rearset plates. These are from Projection Components in the UK, to my specs. "My specs" may be a tad off as it now looks like the pegs are jacked up pretty high. Will have to see how they feel when I am sitting on the bike. If it is off, I might have an idea on how to adjust them lower, by pivoting the plate downwards slightly, and drilling a new hole. We'll see. They also may need to be spaced out somewhat to clear the shock body a bit. I assumed as much, and will get some spacers machined when I get closer to completion.
The front wheel came back from the machinist. It is now centered in the R6 forks, with captured spacers (nice!). The radial caliper is a magura model originally from an Aprilia RX supermoto. The adapter is one available on ebay, meant for an early R1. Some measurements and research indicated it should work, but the moment of truth showed it was compatible, with some adjustments. You can see the spacers underneath the caliper for the oversize rotor; the adapter plate itself also needs to be spaced to center the caliper over the rotor.
You can see in the first pic, a new design of lower shock mount. Here is the mockup for the upper. That's 4130 aircraft seamless Chromoly tubing. The threaded collar slides inside with a nice interference fit which should make welding it fairly straightforward. The plan is to weld that tube to the frame spar, reinforced with some 4130 sheet I also have. This "saddle weld" should be strong enough, considering the total length (9 inches) of "contact" between the 2 tubes. I am farming out this job to my local tig welder expert. You can see the ride height adjustment built into this design.
I was also able to fit the "gutted" engine. You can see the front downtube (I was able to find this rare piece in California), originally intended for the liquid cooled 660 engine also works with the aircooled lump. The header pipes give a sense of exhaust routing as well, but the 2-1 collector, specifically the end, fouls on the frame tube. So, when the engine is securely mounted, and the carbs in place, I'll need to do some cutting and refitting to finalize routing of the exhaust.
Front quarter view. Thankfully I did end up with a mockup engine, as it was heavy enough on its own. The rear engine mount is actually 16mm. Some careful drilling with a 17mm drill bit allowed me to ream it out to fit.
So, once the rear shock has been finish-welded, the next step is to get the bike on wheels, and finish the rear subframe and align the engine and countershaft sprocket to the rear wheel. More spacers will need to be made for the rear engine mount.