wideband O2 tuning

So I ended up buying a wideband O2 sensor kit.  I went with one that displays on my phone (thanks for the suggestion ThatGPZGuy). I just took the bike out for a test ride. Absolutely love this setup and the O2 sensor is clearly going to be very helpful with tuning. I marked the different throttle positions with white paint and took a video of the ride so I could see both the O2 gauge and the throttle position in real time. It's a very easy/nice way to analyze.  This is the setup:  



This is my current jetting (other details about the bike in my signature):
pilot: 40
mains:    98/100
needles: Factory Pro Stage 3, 3rd clip

Amazingly enough I had to go way down on the main jet with the 615 big bore (was at 110/112) and it's still running rich. Here are the AFR's at various throttle positions (+/- around 0.5 at each position): 

idle: 12.6
1/8: 10.4
1/4: 10.4
1/2: 12
3/4: 11.5
WOT: 11.5



Idle seems fine, I don't think I'll change the pilot jets.  But I'm thinking I should go down a few steps in the mains (from 98/100 to 95/98), and switch the needles for either the stock ones or Factory Pro Stage 1 needles (only reason I have the Stage 3 ones in now is because I was experimenting with pods earlier and figured I'd see what the O2 sensor told me before changing them). 

I'm basing these proposed changes on diagrams like this (though they all seem to vary a bit): 



What do you all think?  It's sooooooo nice having data to help decide which settings to try!!!

Nice set up, "lambda1" is 14.7:1 on a water cooled motor with full engine management, on an air cooled like this between 12:1 and 13:1 is ideal without running too lean and risking detonation

That is so cool. I wish I I would have gone with the phone set-up instead of the gauge. Has performance increased as you are chasing the AFR#?  

Zaddict, I had Factory Pro needles in my 810 engine with CVK32 carbs and found same richness in low throttle setting.  Installed slightly thicker zx600A needles that came with the eBay carbs and now it's perfect.  But I have to admit that I really like this phone set up and I've been thinking about adding one to my bike since seeing your original post.  So in the near future I will see how calibrated my seat dyne really is.

ThatGPzGuy wrote:

 Has performance increased as you are chasing the AFR#?  

Most definitely!  And gas mileage keep improving too. 
Given the AFR numbers from my previous test ride I decided to go down to 95 outer/98 inner main jets and to reinstall the stock needles in lieu of the Factory Pro ones.  These are results of the latest run (+/- 0.5 for each reading): 

Idle: 13.0
Off idle: 10.8
1/8: 12.6
1/4: 13.2
1/2: 13.3
3/4: 12.5
Full throttle: 12.5

I think those are pretty ideal? Certainly the bike is running strong, and I hit 40 mpg on the ride, up from a comical 20mpg when I first rebuilt the head. 

One thing I noticed is that I'm getting a pretty severe lean spike when I go full WOT from a stand-still.  Here's a graph of the AFR during a couple such take-offs: 

 

My float heights are set on the lean side (19mm, spec is 17mm +/- 2mm).  I'm wondering if that might be the issue and if the carbs just aren't getting the fuel they need to support off-the-line blasts. Does that make sense? Seems the jets and needles are spot on judging by the static AFR numbers. 

 

Just a thought, it could be that you get a fuel level drop in the carb bowl due to the centrifugal forces under hard acceleration.
 

That looks about as "spot on" as you can hope for with carbs, excellent work. IMHO what you are encountering is the limitation of carbs over EFI, when you snap open the throttle it takes a few milliseconds for the "intake air speed" to catch up and draw enough fuel (this is why some carbs have an "accelerator pump" to plug the gap as the air speed picks up) If it was me I would "stick a fork in it" and call it done 

Wookie58 wrote:

That looks about as "spot on" as you can hope for with carbs, excellent work. IMHO what you are encountering is the limitation of carbs over EFI, when you snap open the throttle it takes a few milliseconds for the "intake air speed" to catch up and draw enough fuel (this is why some carbs have an "accelerator pump" to plug the gap as the air speed picks up) If it was me I would "stick a fork in it" and call it done 

oh wow, I'll bet you're right. I've heard of accelerator pumps but never knew what they were for. I haven't noticed any hesitation or stumbling so I think I'll just stick a fork in it as advised  

Zaddict great setup!!!  I love tuning with afr, takes the guess work out. But never done it on a bike. Where did you mount the bung ? 

Nice readings !!

1kz4me wrote:

Zaddict great setup!!!  I love tuning with afr, takes the guess work out. But never done it on a bike. Where did you mount the bung ? 

Nice readings !!

Yeah, wish I'd done it ages ago - would have saved me so much time dinking with the carbs!
I mounted the bung on the collector, facing the underside of the bike, maybe 8-10 inches from the headers and just before the muffler. I'll post a photo when I get a minute. I was able to mount it so I could still remove the oil filter, and it's basically invisible from 99% of viewing angles.