My buddy races these (vintage motocross). There is actually a lot of power to be had in those motors if you know the tricks. The part that slows you down is the antiquated suspension. He's got one that he converted to a road race bike that is absolutely sweet.
Got a pic of the road bike?
Wally I had one which I put a rd forn-end, European bars, ported cylinders, custom low exhaust fabricatied and a cafe quarter fairing. It would go past the ton with the right gears. Terrible fuel milege with the alterations but loads fo fun.
Nice DT for you downeaster, scroll down a little...
well done, looks good