DISCLAIMER: YOU DO THIS AT YOUR OWN RISK AND MAY VOID THE MANUFACTURERS WARRANTY.

Step 1. Before turning the ignition on press and hold Select and Reset buttons, turn the ignition on and keep holding both buttons until you see the Diag screen appear.

Step 2. Press Select once to toggle to the CO MODE

Step 3. Press both Select and Reset together. Hold for about 3 seconds to enter co mode. The number displayed is the cylinder selected (genereric computer for all Yamahas) You need to select 1, Press select to scroll up and Reset to scroll down.

Step 4. Press both Select and Reset simultaneousley for a few seconds to see the setting for the selected cylinder. This number will be different on every bike and has no relationship to the mixture its just a number it can range from -128 to +128. Write down the number and keep it in a safe place in case you need to return to your original settings.

Step 5. Pressing select will increase the value (richen the mixture), pressing Reset will decrease it.

I initially increased my setting 5 digits from 10 to 15. This smoothed the bike out but still had a little surging. After reading what Alan and others have said it should be safe to increase your original setting by up to 10 digits. I will now adjust mine up another 3 to 18.

Step 6 To exit CO mode, turn off ignition.

Noticed benefits. The bike is now very smooth to ride and on my 1st adjustment took out almost all the surging/jerkiness. This has made the bike much easier to ride through corners where i can now get on the gas earlier in the corner increasing the mid corner speed.


More info can be found on the forum: fueling fix.

I have been playing with the fueling on my Xt660X to improve it's performance & rideability.

I have fitted variable adjustable resistors to the Air temp sender & Coolant temp sender. Adjusted them to lower temp readindgs, of 5 deg C for both. Increased CO from 9 to 28. Adjusted throttle angle sensor from 16 to 22. Removed the snorkel from the airbox & added 2X 50mm holes to the airbox. I still run STD pipes.

The bike rides very smooth now, with a little improvement throught the whole range & not much more in fuel. This might help other riders who can't afford a power comander or local Yamaha dealership that can't get your Xt to run smoother or stop it cutting out.

Seems like you sorted your bike out well, it cost me a fair bit of dosh to get mine sorted ! did you have any problems with the bike cutting out,another of our members has this problem i thought it could be the throttle sensor?

My bike cut out from the very day I bought it. I took it back to the agents a few times, they had no clue what the problem was, that was a year ago. It was very intermittent.

I then started to do a little research on the fuel injection system. I found away to richen the CO through the dash & moved the throttle sensor up in angle & never looked back. No more cutting out

The bike still ran very lean. A few weeks latter I then played with the Temp sensors. Add two variable resistors & that richen it up nicely.

I have also made 2 spacers for the front fork springs, as I have found the front end starting to sag. Spacer size 37mm outter, 25mm thick, with a 20mm hole in the center. The front end feels nice & stiff & has not topped out with the extra spring tension.

Hi kev!

Nice one there. Looks like you have managed to outrun the system with that trick.
It looked almost like one trick we used to try on the Golf GTI 16v. There you have a full throttle switch, wich we runned over a relay with a sertain resistor connected to it so it was fooled to belive that the engine was cold and opened the coldstartvalve. But only when you pushed the pedal to the metal

Please let us know how you did it and wich ohm you used for the air and coolant temp senders so that others could try it

Nice mod

Hi Stoppstadd

I left the motorcycle trade as a mechanic after 12 years & now have work for Volkswagen for the past 14 years. As a workshop foreman. I have been playing with fuel injection systems for a few years now. So the Xt was pretty easy to sort out.

I used 2x. Adjustable resistors from 0 Oms to 1k Oms, rated voltage 50VDC & 0.8 watts. You can get them from you local electronics shop.

I cut the Coolant temp wire green/red in half, just below the fuel tank. Ran two wires from the variable resistor to each end of the cut wires & joined them. IE, the resistor between the cut wires. I did the same for the Air temp sender. IE, the resistor between the cut wires.

I then went in to the dash into zone 5 & 6, then adjusted the Air & Coolant temp sender deg C & found after may hours playing. The best variable for my bike, being 5 degs C below the actual reading. I can turn the resistors to 0 Oms & the bike is back to STD for work, good fuel consumption. Then can adjust the resistors up, in turn lowers the temp deg C, for the weekend mountain racing. I have marked the resistors 5 & 10 degs settings, for quick adjustment. I had already adjusted the CO up some time before I carried out this mod.

Hi,
I have this problem of cutting out also. I changed the TPS sensor but the problem persists. How exactly you changed the CO so that cutting out is stoped? Or you just have to play with the numbers...?

You need to do a bit of reading around the fuelling threads within this forum get yourself familiar with the issues that cause the bike to surge and cut out, no 2 bikes behave the same but generally one time or another they all pretty much suffer from these occasional problems. There are a number of ways to interact with it and one is altering the CO1 level on the diag mode and other will be to fit a fuelling mod such as the Kev Mod much cheaper and similarly effective as a power commander which will be you other option but obviously more expensive, meantime we suggest you alter the CO1 and remove the snorkle or drill extra holes in your air box see again threads on how to do that, allowing the bike to breath better and burn fuel more efficiently.

Hi Kev,
Your advice has been much appreciated since I bought an 05 xtx a few months back, I did the "Kev" mod & altered the CO value & tried changing the TPS value but my bike still banged & popped on a closed throttle from any rpm & the surging improved slightly but remained.
To learn more I installed a O2 sensor port in the header and fitted my A/F ratio meter and went for some rides.
I worked through each mod in sequence and monitored the result.
Each mod produced a slight change in exhaust O2 readings around idle and slightly above but none of the changes affected the indicated fuel mixture at cruise or full throttle !
I tried going both ways on the CO value to the point of stalling on a low setting but still no change on rpm above fast idle.
This data corespondes to the "feel" of the bike as I could only detect changes around idle performance and no change in general engine behaviour.
My bike has hi flow air filter, Yamaha racing pipes and I cut the "crimped" end off each header (4mm) as the flowbench showed significant restriction from that, it was also causing a lot of flow through the ballance pipe which as the headers are paired obviously could not go anywhere.
As many other riders have found improvements from the mods across the entire rev range I am curious why my bike hasn't responded the same but the test rig I used has proven accurate on other bikes / cars.
I'll keep at it until I find some explanation.
Nick, Auck, New Zealand

Hi Nick, welcome to the XT forum, I will try to answer your questions as you have many.

Hi Kev,
Your advice has been much appreciated since I bought an 05 xtx a few months back, I did the "Kev" mod & altered the CO value & tried changing the TPS value but my bike still banged & popped on a closed throttle ( You need to block off the AIS pipe to stop the popping, the popping is mostly caused by air injected into the exhaust port for emission control) from any rpm & the surging improved slightly but remained. What are the last 2 numbers on your engine ECU 00 or 01?
To learn more I installed a O2 sensor port in the header and fitted my A/F ratio meter and went for some rides. Not sure what type of A/F meter you are using is it a wideband sensor, what data logging rate does it use? Y ou need to block off the AIS pipe before you can get any accurate A/F reading. As the AIS valve can open at any time & throw out the readings.
I worked through each mod in sequence and monitored the result.
Each mod produced a slight change in exhaust O2 readings around idle and slightly above but none of the changes affected the indicated fuel mixture at cruise or full throttle ! I use Tunelink software on the dyno & now have a WB2 commander that data logs throttle position as well as A/F ratio from 10 to 18:1 using a wideband O2 sensor for quick on the road testing.
I tried going both ways on the CO value to the point of stalling on a low setting but still no change on rpm above fast idle. You are corr ect, once the TPS reads over 18 on the dash it will run on the fuel map. The fuel map can then only be adjusted by the sensor inputs, coolant, air, air pressure, throttle position & rpm signals within a small parameter.
This data corresponds to the "feel" of the bike as I could only detect changes around idle performance and no change in general engine behaviour.
My bike has hi flow air filter, Yamaha racing pipes I would recommend you to run a Power commander with those mods to gain full control over the fuelling, also add a stage 2 DNA filter for more gains. and I cut the "crimped" end off each header (4mm) as the flowbench showed significant restriction from that, Thanks for the info I do not know that it was also causing a lot of flow through the ballance pipe which as the headers are paired obviously could not go anywhere. The H section is there to improve bottom end torque.
As many other riders have found improvements from the mods across the entire rev range I am curious why my bike hasn't responded the same but the test rig I used has proven accurate on other bikes / cars. Try disconnecting the AIS by blocking the pipe off so you are get a true A/F reading all the time. If you unplug the AIS at the connector the valve will remain open showing a constant lean mixture on the CO tester.
I'll keep at it until I find some explanation. The best fuelling mod by far is a power commander which will allow you to adjust the fuelling through out the rpm range +-.
Nick, Auck, New Zealand

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Mods that I have done to my XTX's

My 04 XTX
Stage 1 & 2 DNA filters / Kev fuel mod / snorkel mod / Drilled air box mod / Engine breather mod / Fork Spacer mod / 15w fork oil /
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My 07 XTX
Raptor 700 cylinder 102mm / Modified Crank Case to take a 105mm Raptor Cylinder / 11:1 102mm JE Raptor piston / Stage 1 Raptor Hot Cam / Ported head / Colder Spark Plug / +2mm Throttle body / DNA stage 1 & 2 filters / Modified Air Box / Snorkel removed / Worry Brothers stage 2 filter cover / 6mm & 8mm Bolts Replaced with Titanium Bolts / Recovered seat in Black / O2 Eliminator /

My 09 XTX
59HP at the rear wheel / Stage 2 Raptor Hot Cam / DNA stage 3 Air Box / Carbon Can Exhausts / Modified Exhaust Link Pipes / PCIII With Custom Fuel Map / Wideband Commander O2 Data logger / LCD100 Dyno Jet display & fuel adjuster / 2500 OHM HT lead instead of a 10K OHM XT lead / Extra Coolant Cooler / Protaper Fat Bars / Tail Tidy With LED Tail Light / OKE Protection Knobs / LED indicators / AIS blocked / Modified rear sprocket rubbers / Rear Foot Pegs removed / 09 ECU With 02 Sensor Changed To A 06 ECU / Complete wiring harnes Changed from 09 to 04 / Home made LED resistor flasher / Hole drilled in the fuel tank filler neck to allow quicker filling / Modified Bar End Weights / Progressive front fork springs, 15W fork oil, forks lowered 25mm, used XTR rear links lowering the rear 20mm, rear spring one click stiffer / Changed front & rear guards from blue to black / 47T rear sprocket / Speedo Healer V4.0 / Kev throttle cam mod / Throttle grip mod / The new 2010 O2 sensor mod is out, works a treat, The new 2012 O2 Controller is out, PM me for details

Now ride a 2018 MT09SP ABS + TCS

My KTM 990 SMR Mod book. http://www.ktmsmt.com/viewtopic.php?f=13&t=4946