How to Adjust Honda TRX350 (TRX 350) Idle Screw

Question

What are the correct procedures to calibrate the idle screw and achieve normal rpm? My Honda TRX 350 engine runs too slowly while out of gear. I want to fine-tune the carburetor idle speed adjustment screw to increase idle speed.

How do I set idle speed adjusting screw? Do I need a tachometer or can I adjust idle rpm based on how it sounds while it’s running? I have heard some people adjust the idle based on how bumpy the engine runs. Also, if I need to use a tachometer to alter idle speed, what should the RPM be at idle?

Lastly, where is the idle speed screw located, where do I get a tachometer and how do I use it? I know it’s a lot of questions, but this is a question answer site. Thanks.

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Benjamin Yue 8 months 2020-12-07T00:30:50+00:00 3 Answers 733 views 1

Answers ( 3 )

  1. Before you adjust engine idle you should perform a tune-up so that 4-wheeler performs at maximum efficiency. Adhere to the vehicle’s maintenance schedule and check the air cleaner element, spark plug, throttle operation, engine oil and filter, etc.

    Engine Idle Speed Adjustment

    How to tune carburetor idle screw.

    Idle adjustment screw/knob location.

    1. Follow maintenance procedures and be certain all items are within factory specifications.
    2. Run the engine for 10 minutes until it reaches normal operating temperature.
    3. Shift the vehicle into neutral position and be certain it is on a level surface.
    4. Use a tachometer to check  idle speed RPM.
    5. IDLE SPEED FACTORY SPECIFICATION: 1,400 ± 100 rpm. (1986 thru 2006 TRX350 models).
    6. Adjust idle by turning the throttle stop screw in either direction in order to achieve desired rpm.

    Measuring Idle RPM

    To properly adjust engine idle you will need an LCD digital gasoline inductive tachometer. This is a simple to use tachometer https://amzn.to/2JHsiA7.
    How to Adjust Idle RPM Honda TRX 350 2006 2005 2004 2003 2002 2001

    To install the LCD tachometer, clip the alligator clamp to the spark plug wire, about 2 inches from the spark plug. The tachometer will turn on and display engine RPM.

    The tachometer comes with detailed instructions. Follow their instructions, not mine.

    Best answer
    • I need to balance the idle on my 2003 Honda FourTrax Foreman 400 TRX400FW. Is the idle speed the same (1,400 ± 100 rpm). Do these same procedures apply? Can I use the same tach that you linked to?

      • Yes, same procedures. You can use the same tachometer. Alter the idle speed slightly, then pause, and continue adjusting it until you achieve the desired rpm. Alter it slowly because sometimes a tachometer will lag by a second or two.

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