Old PTwins you couldn't do a pipe/slip on, exhaust was one of the items specified that had to be OEM stock. Shock could be replaced but had to use the OEM mounts without modification. Forks could be worked over but you had to retain the OEM upper and lower limiting your options there. (Basically SuperSport suspension rules.) Other allowed changes are spelled out in the production rules list, steel braided brake lines are ok, no internal engine mods at all, have to retain a headlight shell and keep the reg/rect plugged in, etc. Section 19 of the rulebook IIRC has the production class rules.
Eric: To keep the crazy fiends (like me) at bay make sure the normal CCS single cylinder blindspot is NOT present for the class. ULTB as written says any engine, any frame may be used if it's a single. CBR250R with a CRF250R motor that's been worked over, legal. Think the CBR's chassis is too heavy, build around a different one, like say a NSR125 one... hello escalation!
Unfortunately, I dunno what to suggest for a class structure that will accommodate the KTM, plus the two Ninjas AND the CBR and have them all be competitive with each other while keeping costs in check. Given what the other series are doing, and the gentlemen's agreement in the southeastern CCS ULTB region I'd start with supersport rules and a list of allowed bikes rather than the normal engine design / displacement binning. Ninja 300 all years, Ninja 250 all years, CBR250R all years and the KTM 390 if it shows up, all supersport and see what develops. Bikes from other orgs will be able to slot right in, and racers from LRRS will slot into the other series. With that base rule structure I'd allow 'motards' based on again specific bikes, Yamaha WR250R, Yamaha XT250, Honda CRF250L, etc. Just restrict them to normal SS wheel rules to start.
(IE 18/16 to 17 conversion is fine, must retain OEM width though.)
Proposed LRRS ULSS Rules:
Kawasaki EX250
Kawasaki EX300
Kawasaki KLX250S
Honda CBR250R
Honda CRF250L
Honda Rebel 200/250
Suzuki GW250
Suzuki DR200SE
Yamaha WR250R
Yamaha XT250
Yamaha V-Star 250
Hyosung GT250 / GT250R
Hyosung GV250
KTM 390
Husqvarna TE310R
Only listed bikes may enter, all other bikes are excluded from the Ultralightweight class.
20.1.2.6 and 20.1.2.7 are waived for ULSS. All other SuperSport rules except where noted otherwise will be enforced.
LRRS reserves the right to impose additional restrictions on specific makes and models as needed to maintain class balance. LRRS also reserves the right to allow additional modifications outside of those allowed by SuperSport rules on specific makes and models as needed to maintain class balance. Make and model exemptions will be announced at the riders' meeting two rounds prior to going into effect.
Gino: LRRS/CCS requires 15" wheels minimum on ANY bike competing, otherwise my, er Sav's pitbike would be out there already.