I own a 92 Polaris and have been over 60mph many times. A friend of mine owned a Su-sucky 500 late 80s I think, 2 stroke he as been clocked at 80+. Another friend owned a honda 250r 3 wheeler which was clocked at over 70+ His brother bought it off of him and did alot of work on the engine gearing etc... He uses it for ice racing and has been clocked at over 100+

There are kits for just about every machine out there that will improve performance it just depends on how much $$$$$ you' re willing to dish out.