Honda TRX500 (TRX 500) Idles Rough


My 2014 Honda Foreman 500 4X4 runs too slowly when disconnected from a load. The idle is uneven and bumpy. Sometimes when I put it into gear the 4-wheeler stalls.

No DTC is blinking so I assume no code is stored in the PCM. How do I set idle speed to make it run smooth?

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Christian 3 years 2020-12-09T01:28:03+00:00 3 Answers 1586 views Beginner 1

Answers ( 3 )


    If I am not mistaken, The Honda TRX500 design eliminates the need to manual adjust idle speed. Although you can check engine idle speed with a tachometer, I recommend this one
    Why does Honda TRX500 idle and run rough?

    If the engine runs rough check the spark plug first. The recommended spark plug for 2014 thru 2016 models is this – NGK: BKR5E-11.

    If you haven’t replaced the spark plug in a while, do it now, or clean the spark plug center electrode with a wire brush or plug cleaner. Use a feeler gauge to gap the spark plug. Spark plug gap: 1.0 – 1.1 mm (0.039 – 0.043 in).

    Next check the air cleaner. You will need to remove the seat and unlock the retaining clips to take off the air cleaner cover. Then loosen the band screw and remove the air cleaner element assembly.

    Disassemble the air cleaner assembly. Inspect the dust cover, clean it or replace it if necessary. You can wash the element and filter with a non-flammable solvent made for this purpose. Allow it to dry before reinstalling it. You should apply Pro Honda Filter Oil or equivalent, follow procedures as outlined in the owner’s manual.

    Check the idle air control valve for correct operation. The IACV can experience a circuit malfunction, replace if necessary. Be certain the IACV connector is tight. Diagnostic trouble code (DTC) 29 indicates a bad IACV.

    Inspect the fuel supply system. Make sure there is sufficient fuel pressure. Turn the ignition switch to the ON position and engine stop switch. Be certain the fuel pump begins operating for a few seconds.

    Let us know if your Honda TRX500 runs smoothly afterward.

    Best answer

    I am having the same problem. My 2006 Honda FourTrax Foreman Rubicon 500 TRX500FA idles too slowly when out of gear with intermittent stalling. How do I set the idle?


      First perform a tune-up i.e. spark plugs, air cleaner, engine oil and filter change. Refer to the maintenance section in the owner’s manual. Then do the following:

      1. Ride the all-terrain vehicle for 10 minutes.

      2. The four-wheeler must reach normal operating temperatures.

      3. Connect tachometer to spark plug wire.

      4. Position ATV on flat level surface and shift it into neutral.

      5. Check idle speed. The idle speed should be: 1,400 ±100 rpm (min·) (2005-2012 models).

      If idle is out of adjustment, remove the recoil starter cover and adjust the idle speed by turning the throttle stop adjustment know in either direction until the recommended RPM is achieved.
      remove tachometer and reinstall recoil starter cover.

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