Ask The Editors: Am I Due For New Rings?
How to know for sure.
It sounds to us like worn rings/ time for a new top end as well. The good news? You can check for this without having to do anything more than taking out your spark plug to perform a compression test. The whole process can be performed in under 10 minutes and will provide an indicator of the condition of the your quad’s valves, seals and piston/ rings.
To perform one, pick up a cylinder compression tester like the one shown above. A ATV-specific set will set you back around $100 but it’s one of those tools you buy once and can use with any machine you own for a lifetime. We’ve also had success running much more affordable motorcycle testers that were only $20 at the auto parts store.
Take the threaded probe and, once you’ve removed your spark plug, hand tighten it into place. No need to torque it with a wrench. Note that this could potentially be the most difficult aspect of the whole process as some ATVs have very little clearance. We’ve had some that we could attach the tool in twenty seconds flat and others that required the removal of the gas tank.
Once you’re connected, open the throttle (and keep it open) while holding the start button and watch the compressor gauge for it to reach peak pressure. Jot down the results. Remember, though, without the spark plug, the engine can’t start. So be sure to hold the button long enough to observe where the gauge peaks.
Now compare this to your factory spec as indicated in the manual. In the case of the King Quad 700, 142 pounds per square inch should be about right.
If your compression gauge numbers come in below the accepted range, it’s time for a new top end. We say that rather than “new rings” because whether the piston itself has worn enough to allow for pressure to escape or just the seal created by the rings against the cylinder wall, you’re going to want to replace both once you have it opened up. Additionally, low compression can be indicative of other top end issues such as worn valve seats, a cracked valve, loose/worn out valve guides etc.
A leak down test can help you more accurately determine the culprit, or, once you get inside the top end, grab your feeler gauges and micrometer to start measuring for the area that’s out of spec.
