I recently ran a compression test on my ’97 Powder Extreme and it read 97 pounds per cylinder. Just as I thought that the motor was junk we tested the neighbors ’97 EXT 600 and his read the same. What gives?
How are you checking the compression? If you’re only pulling on the rope once or twice then you’ll get inaccurate low readings like this. You want to keep pulling on the rope until the compression isn’t going any higher. I hold the throttle wide open (easier to pull over, takes less pulls) and pull on the rope at least five times. The compression will usually peak by five pulls, but if it is still going up on the gauge keep pulling. You could do the check with the throttle closed, but it’ll take more pulls to get an accurate reading. It really doesn’t matter if the engine is warm or cold, but if the engine is flooded you will get a lower reading because the fuel washes all of the oil off the cylinders and the rings won’t seal very good. If the engine is fogged, you will get a higher reading because of all of the fogging oil. Next time you do a compression test, see what kind of a reading you get with the throttle closed and only pulling on the rope twice; then hold the throttle wide open and pull on the rope five times. What a difference!
Is 97 pounds of compression low? You bet it is. You really need at least 110 pounds for the engine to run decent, but perhaps more important is that the readings are all within about 10% of each other. We always record compression out of habit to give us an idea of what kind of shape each engine is in as the miles accumulate.