The classic sled, the scorpion. Pure Cuyuna Range power manufactured in Crosby, Minnesota.  The 440 still holds the under 500cc land speed class record. 

Simple machine, 1 carb and 2 cylinders. Points and plugs, very light and fast. Easy to service, easy to run. Not the most delicate of machines, and certainly not the prettiest, but defined the term "rocket in my pocket" in the 70's and 80's.

Although I can find a faster, prettier machine, I dont think I will ever part with my Scorpion 440 Whip.   

Pic of my 1980 Scorpion 440 Whip on an ice fishing adventures.  She does me good!