Thanks for info guys!
Let's clear up some naming-conventions so we're sure to be talking about same bikes:
1987-1999
NSR250R - street bike with lights and turn-signals. Gentlemen's agreement to restrict output to 45bhp. However, swapping out flash-cards in ECU gave it 60bhp. Not single shared part between this and race-bikes.
1985
RS250RW - factory race bike premiered
1986-2002
NSR250 - factory race bike
2003+
RS250RW - factory race bike - who knows why they changed name? Probably out of nostalgia
Honda
info on RS250RW/NSR250 factory race bikes.
1985-2009
RS250R - production racer sold to privateers. Same bike as factory racer. Comes out of factory with 90bhp and with hot ECU in race-kit, it comes close to factory racer. With magnesium wheels stock. Honda had patent on common airbox for V-engine carbs, which forced Yamaha to use less efficient individual airboxes on their TZ.
Particular bike I'm looking at is
1999 RS250R factory production racer. This NX5 generation got single-sided swingarm and upside-down fork like NSR250 factory race bikes.
I got some good info from guy that actually races these things (referred by seller of this bike). Along with my coach who raced TZ250 professionally in AMA back in '90s. Actual maintenance would be better than manual's, but still quite intensive per season.
I'm through with converted street-bikes for track, it's not fun. I've got over 100-days at track on my CBR600RR and about 6-days on RSV4 thanks to Aprilia-Days. While I can go faster, they're not as much fun as Ninjette due to so much extra weight. Crisp feel just isn't there. I can feel difference between running over nickel vs. dime on Ninjette, not so on those other bikes. Stability electronics just gives rubber-band or puppet-string effect on these big bikes and insulates rider.
Also frame & suspension geometry too much of compromise due to needing to be streetable originally. We've all experienced difference with raising forks 20-24mm. Imagine that improvement several times more! So I want 23-degree rake, 90-100mm trail on ~125cm wheelbase. I may run RS250R for a season, while I build my own custom frame for Banshee engine. Distance between top & bottom tubes determines rigidity and you can build significantly stiffer frame with stressed-member engine compared to narrower twin-spar frame that hangs engine. Ducati got significant improvement in rigidity on their 1098S by going from 28 to 34mm (yet thinner) tubing and saved 3+lbs from frame.
I really miss RZ350 I had in '80s. Never should've sold it, but I wasn't into racing back then. It was kinda unruly street bike.