2008 Yamaha Rhino YXR70FX Factory Service Manual, Page 95Get this manual
MEASURING THE COMPRESSION PRESSURE
bWith the throttle wide open, crank the engine until the reading on the compression gauge stabilizesWARNING
To prevent sparking, ground the spark plug lead before cranking the enginecIf the compression pressure is above the maximum specification, check the cylinder head, valve surfaces and piston crown for carbon depositsCarbon deposits EliminatedIf the compression pressure is below the minimum specification, squirt few drops of oil into the cylinder and measure againRefer to the following tableCompression pressure (with oil applied into the cylinder) Reading Higher than without oil Diagnosis Piston ring(s) wear or damage RepairPiston, valves, cylinder head gasket or piston rings possibly defective Repair