2003 Ski-Doo REV 600 HO

The new baby HO makes 700 class power.
Ski-Doo caught us off guard with five new engines for the coming season. That is a lot more than we expected. The new 600 HO engine was probably the biggest surprise. Fortunately, they were among the first off the assembly line this summer and were available for a quick dyno test.

The new engine is actually built on the 700/800 Series 3 platform. This allows a heavier crankshaft to be used. It also accommodates a longer 73mm stroke. The standard 600 twin's stroke measures 65.8mm.

The 600 HO is the first Rotax 600 motor to use Nicasil plated cylinders. The Nicasil helps manage heat dissipation, which keeps performance consistent and durability high. The port timing has been modified to fit the new cylinder dimensions and meet performance parameters.

The new big block 600 also uses the same eight-petal reed cage as the 700 and 800 engines for higher airflow to the engine. A new pipe was built to allow the new engine to exhale.

All tallied up, Ski-Doo expects the 600 HO to be a real crowd pleaser, at ten percent higher output.

"For those states where a 600cc machine provides a lower insurance rates, we'll see a lot of people turning to the 600 HO Ski-Doos," said 'Doo honcho Jean-Francois Guertin. "This is a real sweetheart of an engine.

In addition to all of the performance enhancing changes to the 600 HO engine, the RAVE valves have been slightly redesigned. The final part of the guillotine slide is narrower than the rest of the piece. This is said to help stave off carbon buildup and reduce the possibility of the valve sticking. "This is a very low maintenance system," said Guertin. "You really only have to clean them once a year. If you use the recommended oil, it also significantly reduces the need for cleaning."

On the Bench
The 600 HO should be a rocket ship in the 600 class. Ski-Doo said it aimed at the class benchmark (Polaris) when it designed this engine. By our testing, it surpassed the Liberty twin by a couple of horsepower. We knew it was a strong runner in our on-snow testing last spring, but we didn't know how strong it really was.
We found 119.8hp at 7800 rpm, with the torque peak of 80.6 pounds right on top of it. "This is an impresive engine package," noted Dynoport's Rich Daly. "The 600 HO very makes good power for its size. It does it on a cold pull and then holds it on successive runs."

Our contacts at Ski-Doo were quite pleased with the results of our 600 HO test session. They indicated that it fell cleanly within the range of variation between production engines and dynos.

"This is a strong motor," Daly concluded in his test notes. "It runs at very low RPM and makes high torque. It should be good on the trail and easy to clutch with its good torque."

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