I know some have debated wear on belt-type engine pulleys, so thought I'd add my experience.
My 1,000cc vee twin rides great, but is a PITA in slow traffic - it 'lurches' along if ridden under 3,000 rpm. Now the fact the engine was originally designed for racing means it has a very light crank. That, plus 9:1 CR and short stroke doesn't help - nor does no transmission shock absorber (wasn't needed for the original intention, but by the time I'd completed the project, I'd given up racing and so it became a road bike).
So, recently I decided to take a look at the primary to see if I could fit a cush drive. The clutch is a highly modified plunger type, so no scope there. The crank pulley I made in alloy, splined onto a BSA cush hub. That offered me a solution. I removed that, bought a steel pulley and bored it out so a cush drive would sit inside. Given the pulley width (36mm) enables the cush to be sealed inside the pulley once the sprag drive hub is fitted, meaning the spline and cams can be lubricated during assembly.
Also, because the new pulley is not now supported across its width, I arranged for the sprag hub to be supported by the spring nut (one can just see the bronze bush in the end of the sprag hub in the photo). Given the terrific strain put on the outside of the pulley when starting, I thought that a must.
Almost finished - here's hoping it makes for a smoother ride in today's crawling traffic (glad I don't live in Wales!)
