Tuning with an o2 sensor, advice/tips?

The coil mod was done last year some time. As I recall I was only getting about 8-9vts to the coils. I have not checked voltage after. However after the mod was installed I started getting these white plugs.

Check again and tell us, there is much debate on this. I would think that if done right it should be a good thing, considering your low voltage starting point. Just wondering If there is an underlying issue causing the voltage drop. Maybe just the nature of 30+ year old wiring.

well shoot here is the link... just at idle and the motor was cold

Nice bike! and really cool O2 setup.

I highly recommend these plug reading links:

www.dragstuff.com/techarticles/how-to-read-plugs.html
www.dragstuff.com/techarticles/plug-pictures.html
there are more links at the bottom of the page.

This one is a little long winded. Scroll down to the last few paragraphs
www.strappe.com/plugs.html

Cheers!

Fuel injection is different than carbs.

Carbs cannot change their jetting due to temp the way a fuel injector can alter it's duty cycle to constantly update its mixture. If you shoot for 14 at normal temp on a carb, idle will be super lean when cold. You'll be on choke a lot longer. (This ability to update is also why fuel injection has an easier time passing smog laws.)

Common carb tuning theory is to get the strongest, stable idle. That is at about 12.5 (for normally aspirated carb motors). That gives the widest margin of error in both directions to allow for the widest range in temp, humidity, and barometric pressure without affecting idle speed tremendously. (Ignition timing needs to be right on as well, to take advantage of this range.)

If you've ever done the full prescribed "Lean-drop" method of idle mixture setting on carbs, you'll find you end up in the 12 to 13 range. At least that is where I end up on most of the KZ's I've done. If I do it on a really hot day, then it ends up leaner on cooler days and vice versa.

By the way, since these small o2 systems are not entirely precise, you should at least do one base-line lean-drop to establish what AFR on your wideband correlates to best power. that is, do the lean drop on the idle and see what the AFR registers. That then becomes your center-point AFR that you tune around to get your operating margin.

Another reason for putting idle around 12 is because when you are cruising, and you close the throttle (while still in gear) the mixture goes very lean. If your idle is around 14, when you close the throttle, it will be around 16 to 18. You can start getting backfires and popping in this condition.

The same can happen if the cruising range (1/16 to 1/8 throttle) is too lean. But usually when you close a throttle you don't close down to 1/16 and hold it there, so it doesn't often become an issue.

Your video seems right on for idle and small blips. It should get leaner as you open up slightly (as yours does). If you whack it far open it should go back rich into the 11's.

I don't remember if youve seen my video's or not, but heres a link:
kzrider.com/index.php?option=com_kunena&...mit=20&limitstart=20

I mounted the gauge so straight up is 13 AFR. That way i can tell about where the AFRs are without looking at it directly.

Yes I remember this thread, it was back when I first decided to tune with a sensor.

If I was left to plug chops and plug reading I would NEVER touch the jetting (to much voodoo for me!)

Re-reading it I am finding a lot of good info!

Tomorrow I will get 122.5, 125 and 127.5 Jets ordered from z1 (3,4 and 5 sizes larger) Hopefully one of those will put me in the top end ball park. Then I will get some new numbers and see what to change next.

I also think I need to raise the needles to get rid of the lean condition between 10-85% but I will wait to see what the jets do for me!

Motor Head wrote:

Check again and tell us, there is much debate on this. I would think that if done right it should be a good thing, considering your low voltage starting point. Just wondering If there is an underlying issue causing the voltage drop. Maybe just the nature of 30+ year old wiring.

I checked my switch blocks today for corrosion, and they looked like brand new (I cleaned them a few years back with contact cleaner and q-tips).

The signal wire to the relay was receiving 9.5vts (key in the run position bike off). The battery was showing 11.5vts (and it looks low on acid... time to add some water I think). The voltage out from the relay to the coil was showing 11.5 (again key in the run position but bike off).


I called Jeff today to order the jets, suggested checking petcock for flow and checking to make sure the vent on the fuel tank is not plugged. I am about to head out for a 10 min ride with my gas cap open....

Back from my ride and it is for sure not the gas cap... today was about 15* cooler than my last day of testing and with the fuel cap open I found the results to be almost 1 point higher across the board.


I am curious as to why my bike seems to want such large jets while other 650s run happily on 115's.

I am cold and wet now; later I will pull the fuel line and see if the fuel flows quickly and without interruption.

hardr0ck68 wrote:

Number one is on the left and four on the right.
Pic 2

Number 3 is noticeably different. I assume you did a very careful check of the float levels. If not, make sure #3 is set right. Also check for any vacuum leaks on 3. Also make sure the mixture screw on three is good and not bent etc.

Have you checked valve lash yet, and compression while hot?

Also make sure your choke plunger (enricher plunger) is sealing properly when the choke is off (on #3).

hardr0ck68 wrote:

Back from my ride and it is for sure not the gas cap... today was about 15* cooler than my last day of testing and with the fuel cap open I found the results to be almost 1 point higher across the board.


I am curious as to why my bike seems to want such large jets while other 650s run happily on 115's.

If the air was cooler, the mixture will register leaner (AFR higher). This can also happen if you don't warm up the same amount. I always ride the same route everytime I check readings. I don't really pay attention until I have a solid 15 minutes on the expressway after about 10 minutes of city street riding.

Pods will really affect the AFR. You have to up jet quite a bit for them. On my 550's with manual slides, I went up to 103 from 94 from pods and a Kerker. Airbox and Kerker requires very little change, but the pods really breathe a lot more, albeit less consistently.

Yeah I noticed that on my way back I was slightly less lean than when I left. the bike was probably just coming up to full running temp. Still, the exercise did prove that my fuel tank vent is not the cause of my lean condition.


What a fun toy this thing is going to be. I finally don't quite hate carbs, they seem more tolerable now!