I own a 2002 Polaris XC 800 SP, and on my last ride I noticed that it would not rev past 7200 rpm. It also seems to be a little less potent than usual as well. A friend of mine told me that sometimes the exhaust valves on these sleds gum up and that could be a problem. So I pulled them apart, although there was a little bit of carbon build up, it seemed to me that they still opened and closed fairly easily. What are your thoughts.
Thunder Bay, ON
There are a host of possibilities as to the cause. Exhaust valves not opening could be the cause due to physical sticking or gumming, or if the bellows (air pressure bladder, that rubber round thing under the valve cover) is damaged then the pressure wonâ€™t build and the valve wouldn’t open. Some of the early VES engines (2002s) were fitted with a bellows that wasnâ€™t as durable as the later ones, so If this rubber thing is black in color it should be replaced with the new style that has a textured material, kind of like blue jeans looking but still a blue rubber. Look for cracks, the early black bellows were prone to cracking and not allowing pressure to build and lift the valves.
This would also happen if the primary clutch spring is sacked. Measure spring free length, or compare to a new one. If your valves are OK, then this is also likely. Being an ’02, simply replace it. Quite common as well.
Another one would be if the water temp sensor is indicating a warm engine temp, then ignition rolls back and limits RPM. There were some sleds with faulty temp sensors, they’d go flukey and then the sled wouldn’t pull RPM, but no light on the dash would come on (till the sensor got really far off). Keep this one in mind as well. It can be ohm checked at specific temperatures.
All of these could be the cause of reduced rpm. Of course, it could be something more serious, but these are some of the more common issues that have been known to occur on the 2002s and should be eliminated.