Installation
Important – If you are not a competent mechanic do not attempt to install this product yourself; have your local dealer install it for you.

Precautions:
•Always let the motorcycle cool down completely before you work on the fuel system.
•Gasoline is flammable! Read all safety instructions in your manual.
•Always clean the area around the carburetor before disassembly.

Read all instructions before installing the Fuel Mixture Screw

1.Most original fuel mixture screws can be removed with a short screwdriver; if there is inadequate clearance you need to remove the carburetor per your owner’s manual.

2.Once you have access to the standard mixture screw, turn the screw clockwise until it’s lightly seated. Make a note of the amount of turns you moved it in.

3.Remove the screw counterclockwise.
NOTE: The spring normally comes out with the screw but it’s very common for the washer and/or o-ring to stay inside. You must verify that the o-ring and washer are located either inside the carburetor or mounted on the fuel screw – do not duplicate the parts!

4.Assemble the Pro Factory Fuel Mixture Screw in the following order: screw – spring – o-ring.

Tip: You can install the Fuel Mixture Screw using the original oem spring, washer and o-ring, or the parts that are already attached to the Pro Factory Fuel Mixture Screw.

5.Once you have the parts mounted on the Fuel Mixture Screw, install it in the carburetor turning it clockwise until it lightly touches the stop.

6.Unscrew the Fuel Mixture Screw counterclockwise the same amount of turns that you recorded earlier.

Adjustment and Setup

•Before you attempt to make adjustments make sure your engine is serviced. It’s extremely important that the piston, rings, valve clearances and the air filter etc are good condition.

•The Fuel Mixture Screw works in conjunction with the pilot jet. If you have the correct pilot jet installed, the engine will run its best in the 1 to 2 turn range. If the engine runs better with the FMS set at less than 1 turn or more than 2 ¼ you should also change the pilot jet.

To adjust the Fuel Mixture Screw and Pilot Jet:

7.Set the Fuel Mixture Screw to 1½ turns out, start the motorcycle and get the engine up to operating temperature.

8.Adjust the idle as low as possible without stalling. Idle speed is a matter of preference, but if it’s too low, the motorcycle will be harder to start, especially when the engine is hot. Most factories recommend 1700 to 1900 rpm

9.Slowly turn the screw in until the engine starts to slow down and then unscrew the Fuel Mixture Screw 1/2 of a turn. The screw should be in the 1 to 2 turn range. If the Fuel Mixture Screw is less than 1 turn, the pilot is too big – install the next smaller size. If the Fuel Mixture Screw is more than 2 ¼ turns the pilot jet is too small – install the next larger size.

Note;
•Turning the screw out makes the engine run richer
•Turning the screw in makes the engine run leaner

10.Replace the pilot jet if necessary and repeat the adjustment from step 8.

Additional items required
•Small Flat Blade Screwdriver
•Med Philips Screwdriver
•Owner’s manual for your motorcycle

Pro Tuning Tips Go to: ProFactoryHoses.com and click on link on the bottom titled:
Adjustable Fuel Mixture Screw for the Keihin FCR-MX 4-stroke Carburetors

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