Wide Band O2 A/F Tuning

[IanDMacDonald]

The original owner of my bike had a MAC system on my bike that he welded O2 bungs on, and tuned the bike via a wide band O2 sensor. Anybody ever think about doing that on their's? I'm curious to know how much of a change in A/F ratio the screw makes in ratio to turns.

[DEEBS11]

You are looking for a 14.7 to 1 fuel/air ratio. When you use a color tune tool that blue color you are aiming for about that ratio in the combustion chamber. When a sensor is in the exhaust section, you are looking for hydrocarbon level or unburnt gas like they do at an emission station. Closed loop fuel injection uses this method in a algorithm to meter fuel with those injectors pulsing away. In the end it's 14.7:1 in the combustion chamber. Not sure what hydrocarbon level is optimal. Too much is rich. Too little is lean. Here is a video on the subject.

https://www.youtube.com/watch?v=31uSmMkUSFg

[motoman]

IanDMac, easiest and correct method of setting mixture screws is start with warm motor, backout mixture screw several turns. Then with motor at idle, slowly turn screw in untill a change is heard from motor or exhaust, at which point STOP. Back mixture screw out no more than a quarter turn. Do other three carbs same procedure. Fuel mixture is now set. This is called the 'lean-drop' method and is commonly used for setting fuel mixture screws on ALL carburators cept for automotive carbs. Those mixture screws use same 'lean-drop' method except when change is heard, then back out mixture screw one to no more than one and a half turns. Following this procedure will have motor running smoothly and A/F mixture correct.

[DEEBS11]

The Honda Drop Method that Motoman mentions is an industry standard and certainly works well. An accurate tachometer is supposed to measure a 50 RPM drop during the procedure but as he stated you can use an ear. I should also clarify the mention of the Colortune tool. This tool uses an easy visual method to adjust the pilot circuit. This is the tool I use in my shop.

https://www.youtube.com/watch?v=Y9t8XhFlKbk

[IanDMacDonald]

Yeah. ColorTune doesn't seem to do much for my bike. I have the full kit. I just pull the plugs, as I did not have much luck with the lean drop method either.

I may throw some new needles in down the road to see if it helps.

[Tonyxs11]

The Honda Drop Method that Motoman mentions is an industry standard and certainly works well. An accurate tachometer is supposed to measure a 50 RPM drop during the procedure but as he stated you can use an ear. I should also clarify the mention of the Colortune tool. This tool uses an easy visual method to adjust the pilot circuit. This is the tool I use in my shop.

https://www.youtube.com/watch?v=Y9t8XhFlKbk

great video Deebs, been meaning to buy one for a while now !!!! come payday i'll invest in one.

[DEEBS11]

Ian, if you adjust your pilot screws and don't get much change your jets might be in the incorrect range. Might need to change pilot jet size. Not sure what color you see with the Colortune. If it is always rich (amber) with no apparent adjustment with the screws, a possible common problem with XS11s is individual filters covering the air jet making the mixture too rich and unadjustable.

[DEEBS11]

I did see you are using your airbox.