CO Numbers and Throttle "smoothness"

I know this topic has been brought up before, but I believe I may be able to help some folks out that are still chasing a choppy throttle. I have owned many bikes, although this is my first fuel injected beast and it's been an adventure trying to sort out the notorious on/off throttle.

Today for the first time in a long time I had the chance to plug my laptop into my computer and run the bike at idle in my driveway, letting it warm up and allowing the Autotune software to start working. I noticed that the AFR level was quite rich, hovering around 12-11. The wideband o2 sensor is not designed for low rpm readings, but it does show a ballpark AFR for idle.

My CO was set to +7. I thought that 12-11 AFR was a bit rich for only +7 CO, so I checked my air filter (no toil air filter). Wasn't too dirty, as in I've seen way dirtier... but I wanted to play it safe. Swapped in the OEM filter which was clean and oiled. Instantly saw the AFR lean out, telling me that either my notoil filter is very plugged or perhaps they just suck...

The CO setting I found to work best was -10. The idle was steady and this gave me an approx 13-13.5 afr at idle. The bike now feels alot different. Coming off idle or fully closed throttle, the bike has way more 'smoothness' I can now actually feel 2% throttle, instead of trying to blast past it or work the clutch to mask the lurch from idle to open throttle. This leads me to believe that the aggressive on/off feeling from the throttle may be due to the situation I had presented for myself, with a combination of a poorly flowing air filter and a CO setting that was too rich for my air flow. Some people have great luck going to high CO numbers. Perhaps that is what creates a good AFR for them. For others with less air flow, as I suppose I am, a lower CO is needed. I had assumed that a number above 0 was necessary to smooth out the throttle but I was incorrect. I don't know if I would have discovered this without an o2 sensor.

Most people look towards the throttle itself, the cables, the TPS. I have done them all. This throttle issue seems to be so common, yet so many mixed results.. Often there is a resolution, or someone claims to have fixed theirs with a programmer and exhaust pipe.,or lubing the cables and adjusting slack. I believe all these things either get you closer to a good AFR at idle, or mask the real problem.

I guess the moral of the story here is after all this fancy tuning and trouble shooting it all came down to setting the CO to the right number. The last thing I expected with all the mods I had was to need less fuel at idle. This was the most effective way to smooth out the throttle, and it wouldn't be easy to determine without an o2 sensor. I suggest trying all numbers, big and small, if you still can't sort out your throttle 'smoothness'

This info should help guys dial in their bikes.

My CO is on 6 but I have the idle turned up to 1900 rpm and run a wide open airbox and pipe. My bike runs poorly off idle when the airfilter gets dirty, I must be borderline too rich but it runs great with a clean filter.

PostSubject: O2 and or CO Today at 7:58 pm Select/Unselect multi-quote Reply with quote Edit/Delete this post Delete this post Report post to moderator or admin Lock post for new reports
I am rather new at this froum, and my 2008 WR250R too owning it for a few weeks, not riden yet, winter!!!
I left my XT660R 2009, mods at the XT, Dynojet O2 controller and a potentiometer in serieal on the airbox temp sensor, open the dash by pushing the buttons gives reading of the air temp, turn the pot meter 5 or 6 dgrs down richening the mixture.
No idea jet about the WR.
Which years WR have and dont have the O2 sensor?

No idea what effect has and in what range pushing the CO up and down.

The potientio meter mod http://www.xt660.com/site/node/136

The WRR's in north America don't have O2 sensors, the rest of the world has them AFAIK.

This is good info, thanks. I wish I had the O2 sensor and tuning software, but I don't so my tuning is all seat of the pants.

I am curious if you would repeat your experiment in different conditions. I think the bike behaves very different in different ambient temperatures. The intake air temp probably affects the AFR. I have played with the CO and found it runs great at like 70 deg F, but when it is cold (below 40) and hot (above 80) I start to have stuttering/bogging at low throttle inputs. Just curious if this is a result of the AFR going off, or something else.

Nobody know's changing the CO, it effects, you can sense it, but no idea what its truely doing.
Only static? Read the VW story!!
Dont think dynamic?
CO is tuning enviroment. Not power.

Fooling the ECU on the temp sensor is an old and easy trick. Works excellent on the XT660R, done worldwide by lots of us. You hog is gone.

Of course when you can spend, buy yourself a package.
Guys over here only say, its not only the package, a dynojet run is needed for dialing in specificly to get it seamless .

The outside air temp has a big affect on what CO setting works best.

I trail ride my bike a bit in the winter with studded tires.
When its below freezing the bike will start and stall a few times before idling on a cold start with the stock CO setting, with it turned up to 6 it starts first try and never stalls, this is what made me adjust the CO in the first place.

I could run it a little higher in the winter and a little lower in the summer but 6 is a happy medium for me so I just leave it on 6.

same i have the dynojet power commander and autotune and changed my CO to -10 so the hot idle is 13:1, runs so much better now.

for those of you who dont know the CO directly adjusts the fuel input idle to 3-4000 so if you have a pcv then keep in mind the CO and pcv can conflict and cause poor performance at low rpm.

tuning isn't as simple adding more fuel across the whole range because stock fueling is both slightly rich and too lean in certain areas. so fooling the air temp sensor would probably make the bike run worse.

Question on the CO settings. I have a new bike 2016 in the US. Do you have to jumper the wire on the lean angle sensor to get to the CO codes.

Is there a setting that anyone can tell me what the factory setting is.

If the Jumper is indeed needed, is there a picture somewhere showing exactly how to jumper the bike.

I bought the service manual, but it is a couple weeks out before my dealer gets mine in.

Yes you do. I don't have an american bike so I'm not sure but apparently unpumping the fuel pump does the same thing as disconnecting the black wire on the lean abgle sensor

My European bike doesnt need the wire. CO setting seems different from bike to bike. Mine is around +6 as I recall.

When I went back to my dealer to pick up my parts for my new bike. I talked with the service dept about my throttle being a bit wild. Mentioned that there was no way I could ride technical stuff with the way the throttle was. they told me it could be a clogged fuel injector due to the stuff they put on / in the bike. anyway they told me to get my 600 break in miles on it and while doing that run some Yamaha Fuel Med through it to see if that would make a difference. if it didn't smooth out, they told me to bring it back, and their service dept would take care of it. I believe what they are saying because this particular mechanic I trust and is good in my opinion. They were aware of the bikes being snatchy, and I think they knew how to fix it. so I'll put in my miles run the fuel med, and then report back. I think this bike will be great once this mechanic gets through with it.

What does the bike come in stock for this