How to Tell if a Jet Ski Cylinder Is Bad

Fortunately, jet skis use simple engines that can be diagnosed fairly easily. They don't require a large engine lifting arm to pull out, so most mechanically inclined people can diagnose a running problem. The cylinder is the powerhouse of the vehicle, and many jet skis use two-stroke or four-stroke engines. So when the cylinder goes bad, so does the jet ski.

Things You'll Need

  • Flashlight
  • Socket wrench and sockets
  • Compression tester
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Instructions

    • 1

      Open the jet ski panel that provides access to the engine. Examine the cylinder area closely and use a flashlight, if necessary, to get a good view. Look for seepage or oil leaks around the cylinder for signs of a failing cylinder gasket. Closely examine the area where the cylinder joins the engine and where the exhaust outlet bolts onto the cylinder.

    • 2

      Remove the ignition wire to the spark plug. Loosen and remove the spark plug in the engine cylinder with a socket wrench and appropriate socket. Insert the screw end of a compression tester tool into the cylinder. Hand-twist it in until snug. Hand-crank the engine with a pull cord to force the piston to cycle through. Perform the test at least three times and measure the reading on the compression tester tool each time. Compare the readings with the jet ski's repair manual for proper compression. Reinstall the spark plug and ignition wire when done.

    • 3

      Connect a hose with a water source to the water injection port in the jet ski. Turn on the engine. Turn on the water source after a few seconds of the water running. Check that the water is flowing out of the exhaust port properly. Listen to the cylinder as the engine is working. Identify any sources of pinging or odd noises that seem like the cylinder and piston are not working correctly. Rev the engine a few times to be sure the cylinder is working properly, noise-wise.

    • 4

      Turn off the engine and hose water if still running it. Let the water drain. Remove the ignition wire and spark plug with a socket wrench. Remove the nuts securing the cylinder head onto the cylinder with a socket wrench and socket. Examine the inside of the cylinder cap for any signs of damage. Examine the piston crown inside the cylinder for signs of burning or holes in the surface. Hand-crank the engine to run the piston through the cylinder a few times to look for signs of friction. Reinstall the cylinder cap and tighten it back in place to factory settings. Reinstall the spark plug and ignition wire.

    • 5

      Check the engine fuel source and oil sources feeding into the engine. Confirm that fluids are flowing properly and that there is no blockage; lack of lubrication can damage the cylinder. Use the socket wrench to pull the spark plug again and examine the tip color. Increase the fuel flow if the tip is chalky white; decrease the fuel flow if the spark tip is oily black. Replace the spark plug in either condition. Put the exiting plug back in the cylinder if the tip is chocolate brown (a good status).