Originally Posted by Kev (Post 1159)

Something else I have done is disconnect the engine breather pipe from the airbox. Blocked the airbox side, fitted a L pipe to the existing pipe, connected a new 13mm ID pipe to the L pipe & routed the pipe down between the swinging arm & the motor. You can get a plastic L pipe from the local hardware shop, irrigation section.

This is so you get pure air into the airbox & not rebreathed engine fumes. Better Air more power.

They only do this for emission control.

Originally Posted by dazzerrtw (Post 55390)

on all our off road Bike's we lift the engine breather into the air box.
some bike's have been knowen to suck water up this pipe when the engine is stalled when crossing water .

could this be a problemif off roading the XT ?

Originally Posted by Kev (Post 66560)

Yes the 07/08 can have there CO1 adjustments altered.

http://www.xt660.com/showthread.php?t=630

Also welcome to the forum.

Originally Posted by JMC (Post 174)

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.

Originally Posted by Kev (Post 74510)

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

Originally Posted by piggar (Post 75200)

Hi Kev, Many thanks for your response, I've been a while getting back to you as I had to repeat all my tests with the AIS blocked to avoid corrupting the A/F results.
That done, the readings I got were a similar trend to before except slightly richer and less changable, mainly around a closed or part closed throttle.
To answer your quetions: my ECU number ends in 01, the O2 sensor I use is a narrow band(0-1v), the logging/response rate of my A/F display is 220ms on bar graph & 440ms on digital display.
The popping in the exhaust has slightly improved and the A/F values I get are around 14.3 - 14.5 @ cruise throttle, and a steady 14.5 @ full throttle, I'm guessing although these numbers may be safe they are probably a little lean for best power.
I re-read your post on HP gains from different mods & attacked my airbox, I'd have liked to put it on the flow bench but did'nt fancy dissmantling half the bike to get it out !
I've drilled x5 holes in the places you show with a couple of changes, I centered as many holes as I could in the middle of the moulded reinforcing so was able to use 38 dia on several (for better or worse) & the two holes on the left side looked like they were being "shadowed" by the regulator so I spaced it out with a couple of 12mm urethane spacers. Judging by the induction racket emanating from under the seat I'd say I've opened things up a bit !
Just to summerise: by trying different settings on the "Kev" mod, the CO value & the TPS, I can make subtle changes to the behaviour of the engine but not enough it appears to counter the changes I've made so your comment about fitting a PC111 to fully optimise these alterations seems on the money.
The main problem I have is the bad throttle response, when on & off the gas an & up and down the gears the throttle response is terrible (compared to my other bikes).
A question if I may, what I/O do the PC111 units modify on the XT, do they use just TPS or several ?
Thanks & Regards,Nick

Originally Posted by Kev (Post 86831)

First of all what year XT do you have? If it was me I would adjust it now.

Originally Posted by hushy (Post 86839)

its a 2009 model 150 miles what do you think:-)

Originally Posted by nein (Post 87684)

I might be wrong but in a bike with several cylinders it can happen that not all of them work at the same temperature due to the fact they get not the same cooling (specially when one cylinder is in front of another one). Maybe this could be something that justified different CO value settings. The headers might also be different which might let one cylinder get rid of the exhaust gases more easily then the other one.

As I am no expert what I have written might just be nonsense. Maybe Kev or Freeze could explain why different CO settings would make sense in a twin cylinder bike.

Originally Posted by PegasoStrada (Post 88309)

We have a Aprilia Pegaso with the same engine and inherent problem with surging etc. There is an oxygen/lambda sensor on the exhaust which obviously reads the air/fuel ratio and sends this to the ecu which I would assume then corrects it to meet the emissions needed to pass the required law. Now if that is the case how does altering the CO achieve anything? I am new to bikes but have nearly 30 years on performance cars and I can relate to remapping etc but does the system work differenty on a bike as modern cars have little or no CO adjustment. Does the CO adjustment only affect idle? Last question, how much improvement does a power commander make?

Originally Posted by bridportblue (Post 91590)

Thanks Captmoto for the :100:
I'll give that a go and see how i get on. If i leave it warming up on tick over it don't cut out, just when i'm riding or coming to a stop. Just done my subscription. Cheers

Originally Posted by weeksy (Post 92525)

Finances currently mean that's not an option, had to spend �100 on a new rear tyre today and also the adjustable XJR brake lever was ordered too.

I was slightly confused as looking at the Dyno figures i couldn't see one for what is now my current setup which is

Snorkel off, CCC's, fuelling adjusted on dash, all filters present.

Not that it really matters.. but was just curious.

Filters will be replaced after end of month when i get paid again :)

Originally Posted by weeksy (Post 92540)

Well after upping the CO1 and removing the snorkel, i can't honestly say it feels any quicker LOL