2004-2005 660 Yamaha Rhino Factory Service Manual, Page 88Get this manual
MEASURING THE COMPRESSION PRESSURE 5 Remove: spark plug Attach: adapter compression gauge 1
Compression gauge PNYU-33223, 90890-03081 Adapter PNYU-33223-4, 90890-04082 7Measure: compression pressure Above the maximum pressure: Check the cylinder head, valve surfaces, and piston crown for carbon depositsBelow the minimum pressure: Squirt few drops of oil into the affected cylinder and measure againRefer to the table belowCompression pressure (with oil introduced into cylinder) Reading Higher than without oil Same as without oil Diagnosis Worn or damaged pistons Defective ring(s), valves, cylinder head gasket or piston is possible