1977 Scorpion BullWhip - with Chaparral 440 engine

This racing snowmobile was purpose-built for cross-country (terrain) racing. Its design emphasized rugged and durable elements to withstand the punishment of long-haul endurance venues. Notice that there are two gas tanks, at either end of the seat.

BullWhips are acknowledged and appreciated by collectors for their sleek, low-slung profile. They were made only one year.

However, the BullWhips had a flaw. The Cayuna engines were innovative with their rotary valve construction that was not a Rotax copy. This design was much simpler and still retained all of the advantages. The engine used machined crank lobes to regulate the fuel/air timing into the engine. The crank lobes were machined to provide .003"- .005" clearance with the inside of the crankcase. The crank lobes also had machined "scoops" on the leading and trailing edge of the crank lobes to improve volumetric efficiency. The rotary valve design allows the intake to open earlier BTDC and close earlier ATDC. This provides up to 200 degrees of intake duration and also allows more time for crankcase compression. All of this adds up to an engine that can pump more fuel through it and deliver a broader power band than a piston port engine which was common in those days.

Alas, the racers were required to stop the engines at the mandatory fuel stops. The heat-soaked engine crankcase had expanded and the tight tolerances needed to transfer fuel upwards into the cylinders were lost. No start - backfire - race over...

So, this BullWhip, like so many others, received a transplanted engine. This example has a Chaparral liquid-cooled 440 engine and some nasty-sounding pipes

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