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 not uncommon 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.
CJR Performance CRF110F Walkthrough
You just picked up your new CRF110F, let’s do some free modifications along with initial recommendations as we work into some cheap modifications.
If you plan to jump or rail ruts with these bikes, first step is longer bolts for the footpeg bracket. I have seen guys actually rip out the bolts from huge jumps as well as catching a rut and physically ripping the bracket from the block. Keep in mind this is a rather rare occurrence but something to be mindful of.
The OEM bolts measure - 18.5mm with the washer (length of shown thread)
Upgraded bolts measure - 25mm (add a crush washer)
Following up low corners, I recommend guys to raise the shift lever 1 spline. I have caught myself in right handers and actually had the bike up-shift on me. This small change can also help prevent a potential bent shift shaft if it were to catch the ground wrong. Raising the shift lever will feel a little odd at first but natural after a few rides.
Shift shaft brace - I personally have run the Kinetic MX shift shaft brace and it has been solid with no issues
ECU - It is important to understand first, the CRF110F ECU does not have any learning trims such as the street models like the Honda Grom/CBR/VTX/etc. The 19+ CRF110F is missing an O2 sensor to read the air/fuel ratio from the head or exhaust. This would allow it to make changes for altitude/modifications/etc. Instead it utilizes a MAP (Manifold Air Pressure) sensor located on the intake manifold to detect engine load and makes fuel changes accordingly. This would be more related to a big guy/small guy and up hill/downhill form of fuel trims. What this boils down to, is with a fixed fuel map, be careful with the choice of modifications without a tune. When adding a generic exhaust to a stock air box, you’ll be seeing around 14.5-15:0 AFR while wide open. We are finding peak power around 12.8-13.2 depending on the setup with this bike so far, all while keeping cylinder head temps down with our revised, more aggressive ignition timing.
Diving into a few free mods - Stock Intake