Adjusting the CO's
I came across this in a write-up on a superbike site. It makes more sense to me than the idea of each CO # being for each cylinder. I have an '08 Grizzly, that only displays CO1. After I made adjustments, I only noticed a bottom end change. I will be testing this theory on the nytro this year.
I believe they would omit the C4 on sleds to prevent a potential WOT meltdown - much as they do when undergearing to prevent overreving (all sled mfg's do it by at least 1 tooth!)
(These instructions are for a 2004 YZF-R6)
A: Fuel injection Adjustment
Fuel injection amount can be adjusted in the following four ranges:
Code C1: Fuel amount injected at 25% or less of throttle opening and at 3000 rpm or less
of engine speed
Code C2: Fuel amount injected at 25% or less of throttle opening and at 3000 rpm or
more of engine speed
Code C3: Fuel amount injected at 25% to 90% of throttle opening
Code C4: Fuel amount injected at 90% or more of throttle opening
Before changing the settings, check the engine for its characteristics in normal condition.
It is recommended that the settings be checked with an A/F measuring instrument.
Guidelines for setting:
• Code C1: At 25% or less of throttle opening and at 3000 rpm or less of engine speed:
This affects the idling stability and the feeling experienced during races.
Too rich an air-fuel mixture may foul the spark plugs.
• Code C2: At 25% or less of throttle opening and at 3000 rpm or more of engine
speed:
This affects the feeling experienced during engine braking and at initial
throttle opening.
Make a change of 2 to 5% at a time while checking for any resulting
changes.
• Code C3: At 25% to 90% of throttle opening:
This affects the feeling experienced at half throttle opening.
Make a change of 2 to 5% at a time and check for any resulting changes.
• Code C4: At 90% or more of throttle opening:
This affects the feeling experienced at full throttle.
Adjustment to too lean a mixture will lead to engine breakdown.
Adjustment by checking the A/F is recommended.
In particular, to adjust on the leaner side, make a change of 1 to 2% at a
time while checking for the result. 12 to 13 is a targeted A/F.