2007 Yamaha Motorsports Grizzly 350 Auto. 4x4 IRS Owners Manual - Page 100
2007 Yamaha Motorsports Grizzly 350 Auto. 4x4 IRS Manual
Page 100 highlights
EBU23211 Checking the spark plug The spark plug is an important engine component, which is easy to check. Since heat and deposits will cause any spark plug to slowly erode, the spark plug should be removed and checked in accordance with the periodic maintenance and lubrication chart. In addition, the condition of the spark plug can reveal the condition of the engine. To remove the spark plug 1. Remove the spark plug cap. 2. Remove the spark plug as shown, with the spark plug wrench included in the owner's tool kit. 1. Spark plug wrench 8 To check the spark plug 1. Check that the porcelain insulator around the center electrode of the spark plug is a medium-to-light tan (the ideal color when the ATV is ridden normally). 1. Spark plug cap NOTE: If the spark plug shows a distinctly different color, the engine could be operating improperly. Do not attempt to diagnose such problems yourself. Instead, have a Yamaha dealer check the ATV. 8-10