IMO, if the Swingarm is modified properly you shouldn't have to change to a 31T front pulley to resolve the tire or wheel clearances if running the Metzler 240 with a 18" x 8 1/2" wide wheel.
Based on my recent DIY 240 mods using the following components:
- Metzler 240/40VR18
- Kosman weld-up wheel 18 x 8 1/2 w/square edge flange
- 33T Road* front pulley using 130T belt
Throughout the physical process of removing metal from the swingarm there was a concern on my part about clearances using the larger front 33T pulley that would displace the front wheel approx 1/4" closer to the swingarm pivot.
Minimal mat'l was removed from both sides of the swingarm to prevent penetrating the welded hollow gusseted castings yet providing at least a nickels worth of clearance when the wheel & tire are positioned anywhere's between full FWD & REV based on the single slotted hole in the caliper mounting bracket which acted as a story stick.
It's very critical that the rear wheel is square and properly aligned in the swing arm and that all component parts in the wheel and hub are assembled properly.
FYI, my mounted 240 Metzler when laid on a flat surface or using a straight edge, only the tire touches and not the rim!
I suspect that there is a difference in methodology amongst the vendors regarding the required modifications to a 240 swingarm and the subsequent clearances
I'm happy to report that i have in excess of 400 miles on my modified swingarm and there is no tire rubbing.
Presidents Day Weekend ride with forum members was a excellent test in the canyon curves.
Enclosing some photos showing various clearances of near completed arm while mocked up during the mod process
Rear Brake Hose Clamp Clearance: Top & Side Views based on Existing Wheel Position using the 33T Road* Front Pulley & 130T Belt. Use of the Yamaha BRAIDED STAINLESS STEEL REAR BRAKE LINE would cut down the profile of the assembly. The Kosman modified wheel has near zero run-out so there is no fear in contacting the clamp unless of course you throw a wheel bearing
View of Caliper Mounting Bracket in the Adjusted position using stated components