How to Adjust the Low & High Speed of the Carburetor of a 1999 Yamaha GP 1200 WaveRunner

According to the maintenance interval guidelines in the shop manual for the 1999 Yamaha GP1200 WaveRunner, the trolling speed -- the low speed for the engine -- should be adjusted every six months or every 100 hours of operation, whichever occurs first. Adjusting the speed at wide open throttle, the engine's high speed, is a more complex adjustment and may require parts replacement. As with the trolling speed, the shop manual recommends checking this parameter every 100 hours or six months.

Things You'll Need

  • Shop tachometer
  • Slotted screwdriver
  • Phillips screwdriver
  • Accelerator pump arm
  • Digital micrometer
  • Accelerator pump body
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Instructions

    • 1

      Launch the WaveRunner. Trigger the WaveRunner's hood latch and open the hood. Attach the lead of a shop tachometer to the engine's spark plug lead.

    • 2

      Tie the wave runner securely in the dock. Fit the emergency shut-off clip in place. Compress the engine enrichment control and start the engine. Allow it to warm to its normal operating temperature. Move the throttle to the trolling speed setting and note the engine speed on the shop tachometer. Turn the throttle stop screw knob, located on the starboard, rear side of the carburetor unit, by hand. Turn the knob clockwise to raise or counterclockwise to lower the trolling speed to 1,350 rpm, plus-or-minus 50 rpm, according to the shop tachometer.

    • 3

      Raise the engine speed to wide open throttle, but do not allow the engine speed -- according to the shop tachometer -- to exceed 7,000 rpm. If the engine, at WOT tries to exceed 7,000 rpm, press the "Stop" button, remove the ignition key and the emergency lanyard clip. Loosen the hose clamps that hold the accelerator pump delivery hoses for carburetors No. 3, No. 1 and No.2, in that order, using a slotted screwdriver. Remove the hoses, also in that order. Remove the four screws holding the accelerator pump-carburetor covers on all three carburetors in place, with a Phillips screwdriver.

    • 4

      Locate the accelerator pump arm, resting on top of each carburetor's needle valve. Remove the pin holding the pump arm and replace the pump arm. Measure the distance from the top of the arm and the carburetor body with a digital micrometer. This measurement must range between 0 and 0.2 mm. Restart the engine. If the engine speed tries to exceed 7,000 rpm after you replace the accelerator pump arm, replace the accelerator pump body.

    • 5

      Replace the accelerator pump-carburetor covers in the reverse order in which they were removed. Re-attach the pump deliver hoses and tighten the hose clamps. Close and lock the hood. Shut the engine down by pressing the "Stop" switch and removing the emergency clip and lanyard from the emergency shut-down switch. Recover the WaveRunner.