I realized I never posted a photo of the rear suspension fully assembled, so here it is.
There are lots of things that could be tweaked and improved, but it’s good enough to move on. Next up on my list is rear engine mounts.
The Bultaco Pursang’s original rear engine mounting bracket attached to the center of the swingarm pivot; that’s not an option with the Yamaha swingarm, and I wouldn’t really want to put any additional stress on that long, skinny bolt anyway. Therefore, my plan is to add cross-tubes to the frame above and below the drivechain path, and then tie them together with vertical plates that bolt to the engine.
You can also see were I will need to relieve the engine mounting bosses a little bit where they contact the swingarm.
The frame is nicely reinforced where the original footpegs mounted. Since they’re too far forward for my purposes, I can cut the brackets off flush and mount the bottom crosstube between the boxed-in sections.
I am planning to use a crossover shaft to adapt the shift shaft on the right to a left-sided shift lever; that may also be able to run through this lower tube.
