The NOS engine was a 200cc but now runs a rebored 210cc barrel, with a machined & ceramic coated jetski piston and modified head taking it up to 240cc with a long stroke crank and water cooling. It has electronic ignition and was engineered by a mate who tunes motocross bikes and race go-karts and built in my shed.
The NOS is a 20hp kit for a snowmobile taking the standard machine from 12hp - 22hp + 20HP of NOS. It only runs a small bottle that gives about 30 secs of continuous use.
Speed wise at the moment it still runs the standard gearbox with a longer 4th gear but goes off the clock in 3rd gear (indicated 90mph) . I can just keep up with it on my R6 (100hp) to 65-70mph when my sis in law rides the scoot with NOS on from a rolling 20mph start.