High/Low Idle after Install - It is generally required to adjust your bikes mechanical idle when installing new parts (like a camshaft* or throttle body upgrade). ALWAYS aim to adjust the idle with a warmed up motorcycle. By default the engines fire up with a slightly richer fuel setting before slowly leaning out to the standard map.
If you bike is idling too HIGH or hangs throttle on decel, you would want to close off incoming air (tighten air screw and/or loosen throttle stop screw)
If you bike is idling too LOW or has poor starting and staying running, you would want to open the throttle settings to allow more air into the engine (loosen air screw and/or tighten throttle stop screw setting).
- Small Idle Adjustments – There is a black air screw located on the left side of the throttle body, the stock position should be 1.5 to 2 turns OUT from all the way in. Anything OVER 3 full turns out, reset the setting back to 1.5-2 and move to the throttle stop screw adjustment listed below. If the black screw makes no changes to idle, the larger idle adjustment is required.
Below is an image of the how the air screw allows the additional air past the butterfly while the throttle body butterfly is in the closed position.
- Large Idle Adjustments - There is a throttle stop screw located by the throttle cables (allen key and a 7mm or 8mm nut depending on throttle body, in the image above it is located at the halfway mark on the line for #3). This set screw is designed for larger idle adjustments and is very sensitive to changes. After setting the idle, return to the black screw for refining adjustments
If you are struggling to get a proper setting, the CJR Air Screw + Idle Screw Combo is a great option to help refine the idle areas. https://cameronjonesracing.com/products/cjr-performance-adjustable-idle-screw
*Ensure your valve lash is set to the recommended setting as each camshaft may differ. Too tight of lash can cause poor cold start or low idle issues.
CRF110F/CRF125F Additional Idle Troubleshooting
The CRF110/CRF125F’s idle is controlled in a few different ways both on the electrical and mechanical. For controlling fuel at idle, the MAP (Manifold Pressure Sensor) at the front of the intake manifold with a short hose), controls initial tip in fuel and early partial throttle fuel from 0-10% TPS (Throttle Position Sensor). If the short hose is kinked, loose at all, or disconnected the bike will not want to hold idle. The brass fitting that comes off the intake manifold has a very small orifice, so even a PINHOLE size air leak can cause the bike to die out with incorrect fuel.
Honda Street Mini Moto Idle Troubleshooting (Grom/Monkey)
For the Honda Street models an ECU reset or TPS reset may be required for low idle issues or any hesitation/hiccups. This will restart the ECU's learning fuel trims and reset them to 0% for a fresh learning start. A TPS reset will re-sync the voltage of the throttle sensor to the grip.
All the Honda Fuel Injected Honda Mini Moto's also have an ECU based setting for a target idle setting based on ignition timing. This means the bike will add or subtract ignition timing to try and meet it's target idle RPM while the throttle is completely closed. This is generally 1,400rpm +/-100.
A slightly higher idle 1,800 +/-100 is often recommended and also helps improve throttle response.