The Sparrow drive belt is an uprated version of the Uniroyal HTD (High Torque Drive). I've been looking through the Cross & Morse timing belt catalogue, which has loads of useful information. Standard belt widths for 8mm pitch are 20,30,50, and 85mm. The Panther RPP belt has three times the capacity of a standard HTD belt and is rated for 30Kw with a 24 tooth primary pulley running at 3000 rpm. Something to bear in mind is that Corbin were pretty sloppy in their fabrication. I've seen an early swingarm where the bearings were purple/blue because they'd welded the bearing housing with the bearings installed! The wider the belt, the more accurate the alignment needs to be (also accounting for flex) and sometimes two narrower belts in parallel will perform better. I'd have the alignment very carefully checked and also have the bearing housing tested for ovality. According to the catalogue, idlers are allowed if mounted on the slack side of the belt, are at least as large as the smallest pulley and have the minimum arc of contact.
Paul Compton BVS technical officer www.bvs.org.uk www.sciroccoev.co.uk
