Honda CRF110
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.
HONDA CRF110F WIRING DIAGRAM 2013-2018
Honda CRF110F Wiring Diagram
Honda CRF110F 2019 Wiring Diagram
Honda CRF110F 2019 Wiring Diagram
Honda Crf110f spec sheet 2013-2018
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ENGINE Engine Type - 109cc air-cooled single-cylinder four-stroke
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Bore And Stroke 50.0mm x 55.6mm
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Compression Ratio 9.0:1
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Valve Train SOHC; two-valve
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Induction 13mm piston-valve carburetor
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Ignition CDI
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DRIVE TRAIN Transmission Four-speed with automatic clutch
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Final Drive Chain
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Front Suspension 31.0mm telescopic fork 3.9 inches of travel
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Rear Suspension Single-shock; 3.4 inches of travel
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Front Brake Drum
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Rear Brake Drum
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Front Tire 70/100-14
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Rear Tire 80/100-12
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DIMENSIONS Rake 24°25' (Caster Angle)
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Trail 52.5mm (2.0 inches)
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Wheelbase 41.9 inches
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Seat Height 26.3 inches
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Curb Weight 163 pounds (Includes all standard equipment, required fluids and full tank of fuelready to ride)
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Fuel Capacity 1.1 gallons, including 0.3-gallon reserve
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Ground Clearance 6.9 Inches
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.
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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)
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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.
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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
As we remove the airbox lid, we find a rather thick foam filter with a mesh backfire screen on the opposite side. We found the foam was a bit saturated from the factory. So we wringed out the excess oil and removed the backfire screen. From here, the OEM intake tube is extremely restrictive as it begins with a velocity stack style funnel from roughly a 2” stack and works it way down to 21mm where it meets the throttle body.
With the smaller exit for the intake tube, we found it to be a large restriction for the stock airbox. We cut and replaced the hose with a 1.5” ID 180* bend HPS silicone hose and 1.5” aluminum adapter shown in the photo above. This generally runs around $50-$60 in parts. Video of the CJR DIY Intake Mod can be found here - https://www.youtube.com/watch?v=FamPPs2pbmI Here is a bone stock 2019 CRF110 baseline before and after the modified intake. The DIY intake is designed for more performance in the mid-high rpm areas, however will reduce throttle response and very low (under 4,000rpm) performance.
For more low-mid range performance increase, we recommend freezing the OEM tube and using a hot knife to cut the 19mm hole to a larger 25mm inlet. This will work great for both stock up to 27mm throttle body options that use the OEM 38mm OD.
As you can see, it does open up the midrange and top end a ltitle bit. From the graph we can see at 7300rpm we go from 5.51hp to 5.8hp and carries a few 1/10ths to redline. Although it does not seem like much, it is a 5% increase in the midrange and 7% at 9,000rpm (4.38hp to 4.69hp).
You can use this calculator to decipher the percent of increase. https://percent-change.com/
NOTE - If you upgrade the throttle body to 24mm, upgrade the hose as well! Otherwise you will have a 19mm tube to a 24mm throttle body. That’s almost a 20% reduction in size.
Throttle Body - Once down to the throttle body, the 21mm entrance of the intake tube, drops down to 19mm at the butterfly. With our ported throttle body, we can open up the opening of the throttle body from 21mm to 31mm however it retains the 19mm butterfly of course. The 19mm throttle body is a restriction itself as the cylinder head port is 20mm.
After separating the intake manifold from the throttle body, we found one of the biggest restrictions of the bike. - The stock intake manifold starts out at 24mm and works it’s way down to 13mm. It then widens back up to just over 20mm. We fix this by adding the cast 26-22mm intake manifold to remove the restricted OEM manifold.
We went ahead and dyno tested both the stock manifold and 26-22mm back to back. We tested the upgrade manifold with both the stock 19mm throttle body and 24mm throttle body. We welded on an O2 bung so we can use the O2 sensor from the dyno to monitor AFR.
Above - We’ll continue off the DIY intake on the blue line, still a stock bike. Next is the red line in which we ONLY change the manifold, still using the stock 19mm throttle body. The bike runs way too lean and needs more fuel which explains the lack of power. Green is spending some time with tuning, only change is fuel adjustments. Orange is adding the 24mm throttle body with additional tuning time over the 19mm. One thing to note is the 5% loss in power leading to 5,000rpm in exchange for the mid-high rpm gains.
Power increase - Instead of making peak power at 7500rpm, the new peak power with the 24mm throttle body and unrestricted manifold comes up to 8800rpm. Notice we also increase the rpm limit to 10,300.
Percent of change - 29.3% increase in “peak power” from the stock intake manifold/throttle body to the 24mm stage 1 kit. Yet if we look at the black line of 8800rpm, there is a 56.25% increase.
Below - I removed the toque numbers as it crowds the graph a bit. However brought AFR in so we can analyze further data. As you can see the red line in the lower graph the bike gets leaner as we go deeper in the RPM. Unlike most bikes that prefer peak power around 12.7-12.8, we find the CRF110 really likes peak power around 13.2-13.4. Our off the shelf maps generally will stay a touch on the conservative side around 12.8-13.0.
Below is testing a few different airbox configurations. Intake lid on vs off as well as with and without the air filter.
Exhaust - Now that we have finished up with some tunes with various intake options for the stock exhaust. We’ll dive into some aftermarket exhaust testing. So far we have a Yoshimura RS9T and a Pro Circuit for the 2019 for testing. I really like the pipe diameter on the yoshimura just looking at the two out of the box. I feel that will play a roll when we dive into larger power. I can see where we will need a larger exhaust beyond both of those to take full advantage down the road, however we’ll cross later.
DYNOS COMING SOON -
Injector - The OEM injector utilizes an 80cc Keihin injector, this is a huge injector for the stock configuration and can last your build for quite awhile. We find the stock injector to max around 13hp, and we generally bump up to the 110cc injector (roughly 25-30% more fuel) around the 12hp mark. During dyno testing of injectors at 12hp (intake/exhaust/132/26mm tb kit/cam) this drops duty cycle down from 90% with the stock to 75% with the 110cc/yuminashi 120cc. The key with injector choice is a duty cycle goal of 70-80% but not exceeding 90%. An injector is a crucial part of the build and MUST be tuned for the injector you are running. The next step up we find the 130cc injector from the PCX150. This is a great option we find works best from 15hp+.
With that said, a 10hp build can easily be tuned with the stock, 110cc/120cc or the PCX injector and likely see the same output across all 3. Sometimes with certain builds there is a benefit to different injectors while other times we do no see an increase.
Cylinder Head/Valves/Springs - The stock valves are very efficient even on the big bore builds. We do see an average .5hp increase in the mid-top end with the big valve kit. We find the stock valve springs to max around 10,300rpm on most camshafts and up to 10,800rpm on other camshafts. An upgraded valve spring setup on these builds is a great addition as this is an engine that really likes to scream.
Port wise we find solely a casting cleanup alone (no reshaping) often sees a 10% increase in top end gains and allows for slightly better overrev. The race head with the 25mm port generally sees a 15-20% increase in top end with much more overrev power available.
Piston/Cylinder - The piston runs a very low compression setup down to 9.3:1. We find a high compression piston alone such as the DHM piston, sees an average 10-15% across the entire RPM range, with much better throttle response and low end grunt. The wiseco +2mm setup is about the same bump again, coming in next with an average 20% increase across the RPM range. The +2mm kit is one of my favorite builds and still retains the OEM cylinder which makes for a great sleeper kit. The 132cc big bore kits, depending BBR/TB we find to have an average 30-35% increase in power across the rev range. (All factors based on intake/exhaust/throttle body/manifold upgrade). We did find the TB132 on the thin gasket option saw knock issues with pump fuel however was a great paired option with race fuel. The thick gasket really took away a lot of the throttle response but still gave the bike plenty of grunt when getting into the throttle. The BBR132 kit we found safe on pump fuel and seemed to split the compression of the thick/thin gasket option of the TB kit.
Suspension - The 2019+ model runs .25” longer shock and front damping rods versus the previous model years.
More information coming soon!