2002 mx z x 800

Ski-Doo's 800 twin won our respect and admiration as a hard runner last winter. We tried it in the MX Z X, Summit Highmark X and Renegade packages. Everywhere we encountered the engine, we were impressed with its relative ease of starting and smooth operation. Not to mention the strain it put on our arms coming off the line. When you pull the trigger on the Rotax 800, you had better be hanging on tight.

Coming into this season, Ski-Doo engineers made other changes to the power plant. There is a new cooling system in place, which routes the hot water through the TM 40 carburetors before heading through the radiators out back. 'Doo reps told us they advise shutting the carb heater circuit off when temps get over 38° F.

In addition to new pistons, there was a rolling change to new machined heads and combustion chambers atop each cylinder on the '02 production line.

A brand new NGK spark plug is in use on the 800 twins this year. According to tech guru Gordie Radtke, the plug is more detonation resistant and is required for optimum engine performance.

Consumers who bought models with the Digital Performance Management system will find it's been recalibrated to be crisper.

The exhaust system has been revamped slightly to make the engine less finicky about carburetion. The silencer box was enlarged to make the sled even quieter. Additionally, the inner dimension of the outlet pipe was expanded to let the engine breathe easier.

"Of all the changes on the engine, I think the bigger pipe outlet is the most noticeable," commented dyno tester Rich Daly. "It makes the engine all the more forgiving on jetting. We only gained three or four horsepower going from stock jetting to our best setting. Usually we see more of an increase in the range of five to seven."

We had an MX Z 800 Sport on the bench as our test unit. We ran it for the requisite eight hours to burn through the break-in chip. The Sport sled does not have DPM onboard, however, for the purposes of our test, the DPM would not have made a difference in the results. DPM only corrects the jetting slightly richer or leaner than jets installed, based on conditions changes. We continually jetted down until we lost power, and then came back up to the peak spec for our test conditions.

In the end, we found that the 2002 800 Rotax twin was almost a mirror image of the '01 model, pulling 134.8 horsepower at 8000 rpm. Its torque band is broad and rather flat above 88 pounds from 7100 to 8000 rpm. "This motor is very consistent," added Daly. "It is going to make the same run back to back to back."