Czech made Jawa Model 870 engine (only one in the U.S.). Used in Europe for sidecar Moto-Cross and roadracing.
1 cyl., 625cc, 4 valve OHC (beautiful head porting), liquid cooled, 6 speed transmission, 11.2:1 compr., approx. 80HP.
I can't help it - I love thumpers!
Eventually will get larger valves and valve seats; along with longer cams, and 15:1 piston.
Main stumbling block (as I'm sure all too many racers know) is $$$.
Maybe our president will offer a motorcycle racers bailout plan.