Carburetor Tuning, adjusting the idle mixture
Sunday, September 09 2007 @ 11:02 PM ICT
Contributed by: news
The first step in tuning the pilot circuit is, or any, carburetor is to get the idle circuit correctly adjusted. That means adjusting the idle mixture screw for the best idle. Keihin carburetors sets the idle mixture screw during assembly and seals the screw under aluminum plug to prevent an owner from changing the setting.
If the aluminum plug is removed, which can be done by carefully drilling a small hole in the plug, threading in a small screw, and then pulling out the plug, gently turn the adjusting screw all the way in until it bottoms. Then turn it two and a half turns out from the fully closed position.
Next, start the engine and bring it up to operating temperature. With the bike in the vertical position and the idle near 1000rpm, turn the idle mixture screw in slowly until the idle either slows or becomes irregular. Now turn the screw out until the engine again slows or begins an irregular idle, counting the number of turns between the too rich and too lean positions.
If the aluminum plug is removed, which can be done by carefully drilling a small hole in the plug, threading in a small screw, and then pulling out the plug, gently turn the adjusting screw all the way in until it bottoms. Then turn it two and a half turns out from the fully closed position.
Next, start the engine and bring it up to operating temperature. With the bike in the vertical position and the idle near 1000rpm, turn the idle mixture screw in slowly until the idle either slows or becomes irregular. Now turn the screw out until the engine again slows or begins an irregular idle, counting the number of turns between the too rich and too lean positions.