CRF110F Technical Data

CRF110F Idle Troubleshooting

Idle - The CRF110F’s idle is controlled in a few different ways both on the electrical and mechanical. For controlling fuel at idle, the MAP sensor (the 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). 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 office, so even a PINHOLE size air leak can cause the bike to die out with incorrect fuel.
- Next are the 2 mechanical ways to control the idle. The first being the air screw, this is a black screw located on the left side of the throttle body. The air screw is designed to allow a small amount of air past the butterfly while the butterfly is closed. The OEM location is to close the air screw fully by turning clockwise until it stops. From the stopped position, make 2 full rotations counter-clockwise (360* total). For small idle adjustments, allow the bike to warm up to operating temp, we then recommend 1/4 turn at a time as this screw is rather sensitive. 1 1/4 turn at the most closes position, and 3 turns at the most open position. Anything outside of those ranges, will require the next step.
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.

The last part of the idle adjustment is the throttle stop screw on the right side of the throttle body. (Looking at the image above, you can see the number (3), halfway across the arrow is the threads of a bolt) When looking at the left side of the throttle body, youo will notice a small nut with an allen bolt that disallows the butterfly to close any further, or allow it to open slightly more for additional air. On aftermarket throttle bodies, it is common to completely remove this stop screw. If the idle is too low with the air screw at 3 full turns out, reset the air screw to 1.5 full turns out, and adjust the throttle stop carefully as small 1/8 turn adjustments can have a large impact. Once this has been adjusted, re-adjust the air screw to fine tune the idle.

AFTERMARKET CAMSHAFT - if you are running an aftermarket camshaft and experiencing low idle, it is common to need to adjust the throttle stop and idle screw to allow for more air and help increase idle rpm.
NOTE: Slightly overnight valve clearances can cause hard starting and idle issues. Due to the high rocker ratio profile of the camshafts, a looser adjustment .005/.006 up to .009/.009 is recommended for most camshafts.