Tuning with an o2 sensor, advice/tips?

Got out for my first ride with my innovate lC-1 working flawlessly! The results...

At idle 11.5-12.2 range so it looks like I will be dropping a pilot jet size or two.


At WOT 14.5-14.9 (I went deep into the red a few time while watching the o2 sensor and not the tach! note to self, no MP3 player while tuning!). That makes me think I should go one main jet larger.


Now for the tricky bit, from idle to about 10% throttle I am seeing a perfect 13-13.5, but anything from about 10%-85% I am seeing very lean 17-18 I even got it to hit 20 a few time... these were readings at speed with a steady throttle (not just after I had whacked it open or slammed it closed). So what do you all think? The larger main should help a little, but I will probably need to drop the clip notch or two down on the needles huh? (bummer I just synced the carbs!)


Keep in mind I am only estimating throttle positions, but the results were fairly repeatable.

Wondering, single wide band O2? Mounted after but how near your collector, if 4-1?
Pic's?
Sounds like the needle is lean.
What is the set up, on /bike/ Mods/ carb size /altitude/ etc?
Are you doing any plug readings as well?
How about mileage readings or time from A-B?

The bike: kz650 w/pods and 4 into 1 (from a zr7-s) the bung is about 3" behind the collector. One sensor for all four cylinders is not perfect for tuning but such is life...

Carbs vm24 without accelerator pump
Main jets are 117.5
Pilot jets are 15
Clip position unknown

float position was a bit high when I last checked it with the proper tool. So I raised all the floats a hair when I had the carbs off this week; but I have not checked the level with the tool since (The float level tool is MIA). When I find the tool I will re-check.


EDIT: I installed the wide-band so I would not have to look at the plugs. To me that is alchemy I prefer science. However the last set of b8es came out sooty on the outside and white on the insulator. I have not pulled these plugs yet.

If not already, make sure your plug readings are all the same, 1 rich or lean will effect the readings at the collector.

Even if one plug is blacker than the rest, what would that change? I have never heard of anyone jetting a rack of carbs differently except in the case of big block's...

I can check tomorrow... It is dark and raining out now.

Well I would look to other reasons if 1 was blacker, float level 1st, possible loose jet, miss sized jet i.e. poor quality control. Leaking choke plunger, if the carb has this. If 1 was really lighter, vacuum leaks as well as low float level, smaller sized jet from quality, restiction in fuel pipe/ hose/ filter/ screen, as the farthest from T fitting will starve first.

The jets are all new from z1 (not to say they must be perfect), new fuel line this year, new glass fuel filter with a nice clean element, 3 year old manifolds that show no signs of cracking or age. I will still pull the plugs to make sure everything is close tomorrow.

Lets assume for tonight all plugs look similar, am I right to say one size smaller pilot, one larger main, drop the clip probably 2 notches, fresh plugs and take it for another ride?



As I understand it the bike should be at about 14-15 at idle and in 13ish everywhere else.

Sound good to me, someone else might chime in, would be good to know altitude as this makes a lot of difference on size, for those who would suggest a set up based on yours.

I am in Presque Isle Maine, Wikipedia says 534ft above.

Ah seal level horse power!!!!!!!!
I'm a mile high and loose around 30% of anything made. An increase in compression or a turbo is needed here, and sea level jetting is to rich. But an average engine will handle more initial and total ignition advance, due to the lower cylinder pressures.
Post up some pic's of your set up/ bike if you can.

hardr0ck68 wrote:

anything from about 10%-85% I am seeing very lean 17-18 I even got it to hit 20 a few time... these were readings at speed with a steady throttle So what do you all think?

The needles call the tune in that region. You either need faster taper or shift them up to get a richer profile.

This is what I bought 5 years ago...