I've got the Clymer manual for my new-to-me 1993 XR600R sitting here in front of me, and a task for myself after experiencing some hiccuping power while on the highway this morning. I'd get intermittent failure of the bike to deliver power on a combustion stroke, at 5500 RPM and higher. This resulted in some stuttery cruising on the highway on the way to a ride this morning. I've owned this bike for a little over a year and I've so far focused my maintenance tasks on tires, oil changes and a speedometer install. Never been into the engine itself thus far. I can find TDC by inserting a chopstick through the sparkplug hole and watching it rise/fall as I cycle the piston from the left side of the motor. I see the intake valves rise during one cycle and the exhaust valves rise on the second cycle. My Clymer manual says: I've rotated the engine probably 7200 degrees so far, and the rockers have no free play. Unless I don't know what "free play" means. What is meant by "free play" in the rockers? Them sumbiyatches are tight and have no rattle to them at all.