Removing idle mixture screw plugs

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The EPA mandates plugs on the idle mixture screws on carbs, to keep you from adjusting them yourself. This is easily taken care of, however.

Idle mixture screws before.jpg Idle mixture screws.jpg

The process is pretty simple:

  • Remove the gas tank, then the side covers.
  • Remove the screw that secures the throttle cable bracket and remove the throttle cables.
  • Drain the gas from the float bowls.
  • Remove all four intake boot clamps by removing screws and slightly bending clamps to get them off.
  • Remove choke cable by pushing choke plunger bracket (on carbs) over and working cable off.
  • Remove vacuum line to EPA canister (California models).
  • Use a large screw driver and pry rubber boots off of the intakes on the head. Then, use the screw driver to flex the intake boots so you can remove them from the bike.
  • Pull carbs forward away from the airbox boots; remove carbs from left side of bike.
  • See here for more information on carb removal and re-installation.
  • Drill out the plugs that are covering your idle mixture screws. These are only about 1/8" thick, so be careful. Drill a small hole in the plugs.

Idle mixture 03.jpg

  • Insert a small (sheet-metal type) screw in the hole, then grab onto the screw with a pair of pliers and pull out the caps.

Idle mixture 04.jpg

  • Set mixture screws to your desired setting. (Be careful when turning the screws in; they don't need to be tight, and you don't want to mess them up. Go with a light touch.)
  • Soak intake boots in hot water to soften up, then install carbs into airbox boots and push carbs and airbox aft as far as possible.
  • Install warm intake boots between carbs and head.
  • Attach all cables, hoses and clamps and double check your work.
  • Make sure that airbox is slid forward back into the proper location.
  • Install the tank, fuel and vacuum hoses, then the side covers.
  • Start bike and warm up to full temp by riding. Adjust the idle speed and fine-tune the idle mixture once warmed up.

It looks like a lot of steps, but it's actually not that hard. Unless the settings were right from the factory (not often) the bike should run better than it did before. If your bike has a hard time settling on the same RPM all the time or has other weird idle quirks, then this procedure is recommended.