I’m calling my new Montesa project “El Fènix,” since it seems to be rising unexpectedly quickly from the ashes of the stillborn Aermacchi-Ducati Special. I offered up the rear wheel and shocks, and the existing parts continue to fit the King Scorpion frame fairly smoothly.
The rear wheel fits the Yamaha SR250 swingarm almost perfectly by eliminating the spacer on the right (brake disk) side. I actually had to spring the rear arms apart about 1–2mm, but I can shave a little bit off here or there to make it a slip fit. There’s a metal blade on the right that originally engaged with the SR’s brake hub that will need to be removed.
Since I removed a spacer on only one side, the wheel now sits in the swingarm slightly to the right, but there’s still plenty of tire clearance, and there’s room to offset the swingarm to the left within the frame far enough to align the wheel with the bike centerline. At least that’s the case according to my half-assed preliminary laser check.
One minor issue is the rear shock spacing. The width of the shock mounts on the swingarm is about 1-1/2″ wider than the upper mounts on the frame. Unfortunately, the frame used two welded steel brackets inside and outside of the shock eye to bear the load. The outer braces were right in the middle of where the top of the shock needed to sit, so the cutoff wheel came out off they came.
I added a 3/4″ spacer to mock up the shock fitment, but obviously some sort of extra reinforcement will be needed. Also, the offset swingarm means that the shocks won’t be pefectly symmetrical to the frame, so the spacing will vary slightly between the two sides.
Overall, however, the obstacles that have arisen are minor. That there haven’t been any real show-stoppers at this point is as much as you can hope for in this game.