Yup, back in the 80's before the term "Supermoto" I used to road race a bike in the AFM "Formula Singles" class at Sears Point in Sonoma CA.
Frame - Yamaha XT 500
Triple tree - Yamaha XT 500
Forks - Kawasaki KZ750
Swing Arm - White Bros
Shocks - Works Performance custom
Front brake - Kawasaki KZ750 disc/caliper
Rear Brake - Yamaha XT500 drum
Brake pads/shoes - EBC
Rims - Sun 2. 5" front 3. 0" rear
Spokes - Stainless steel
Seat - Corbin custom
Tank - XT500
Tires - Metzler "R" compound
Motor - XT500 with lightened flywheel and all the usual flattracker HP parts.
Exhaust - Pipeline custom
The bike was incredibly fun on the track or street. I used to love to head up highway 9 out of San Jose and humiliate all the high $ sport bikes. I would pass them coming into corners at WOT after they started grabbing brakes to set up for the corner. My ridding buddy used to laugh his a$$ of watching them get very squirrelly trying keep pace with the "dirt bike" that had just blasted past them into the corner.
The bike was 300lbs wet and could be ridden like a road bike until it got loose and then ridden like a flat tracker. The brakes were so good it would lift the back wheel braking for corners.
The motor was pumped due to all the parts available at the time for Yamaha flat track race bikes. The tire would leave a little black mark on the pavement every time the spark plug fired coming out of slow 2nd gear corners

Problem was the vibration was so bad in 2nd gear it would literally blur your vision Oo.