Adding An O2 Sensor - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 6 (permalink) Old 05-02-2019, 06:27 PM Thread Starter
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Adding An O2 Sensor

Anyone ever add an O2 Sensor for tuning the carbs?
What about welding in a bung in the top of GB to get both sides with one sensor?


'89 VN750 Bought stock 4/12/18 @ 17805.9 miles $800. Wrecked once. 27454.5+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB. 110/90 Front Tire. Pick-up coil mod. Shindengen MOSFET FH020AA r/r. USB Outlet + Voltmeter. Repainted Metallic Blue w/ new tank bages. Ear Shave (wo/ coasters) 40/140 NO shims 45MPG. MCCT conversion.

Planned modifications:
Custom LED turn signals. Windshield. Highway Pegs. (Possible) ignition adv. Tuxedo Mod. Ignition coil mod.
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post #2 of 6 (permalink) Old 05-02-2019, 10:51 PM
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I am guessing the GB would be too far back to work well. On cars its usually within a foot or so of the head to keep gas temperatures high enough to function and they are usually heated to give consistent results

But really the big question is why? Adjusting the mixture on the fly is impossible, so the best you can do is take readings and jot down the numbers before re jetting in which case a portable o2 meter would do the trick. Or you can pull out a plug and look at the color for a lot less money.

'99 Vulcan "Victoria"
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post #3 of 6 (permalink) Old 05-03-2019, 11:15 AM Thread Starter
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The why, is because I want to know how rich or lean I am.
When I see a list of Rich or Lean symptoms like this list below, I have NO CLUE if I'm rich or lean.

Rich:
Poor power output
Responds to throttle, but sluggish
Lean:
Poor power output
Sluggish …hesitates when the throttle is opened, then recovers (often accompanied by a slight backfire)
Vague throttle response

It has the same symptoms listed for both conditions!
For someone that didn't see his first carburetor until 25, it all seems like black magic to me.

Plug reading is an art.
On this chart https://www.miniplane-usa.com/tips/sparkplugs.htm, I don't see a difference between 3rd row rightmost and 2nd from right 2nd row.
I'm not sure I could recognize a difference between 5th row leftmost and 1st row rightmost.
Additionally, spark plug reading is only valid at one condition.
I could idle for 30 minutes, check the plugs, cruise for 30 minutes, check the plugs, WOT for 30 minutes, check the plugs etc.
With an 02 sensor and a gauge, I can dial in the idle screws in one idle session.
I can go for a ride and get a number for idle 1/4, 1/2, 3/4 and WOT in the length of a city block.

I can also quantify how much a jet size change affects the readings.
For example, lets say 1 size up on main takes me from 16:1 to 15.2:1 at WOT.
I need to go up 6 more sizes to get to 11:1
Drop in a 148 and verify. Full tune in two carb pulls, maybe three.
(From what I read, 148 is excessively large, but this was just an example).

I'm currently at my 4th carb pull, and I'm guessing that I'm still lean.
I'm not sure if I should go to 40/138, 40/140, 40/142, 42/138, 42/140, 42/142.
Not counting changing the shimming on the needles, I am looking at as many as 6 more carb pulls just to check different jet combinations.
At least I'm down to 30min to remove the carb. First attempt took 3 hours!

Lastly, a continuous live reading can help diagnose other issues.
Poor fuel delivery, weak spark, vacuum leak etc.

The real reason why...I'm sick of pulling the carbs and I'd rather be on the road.


'89 VN750 Bought stock 4/12/18 @ 17805.9 miles $800. Wrecked once. 27454.5+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB. 110/90 Front Tire. Pick-up coil mod. Shindengen MOSFET FH020AA r/r. USB Outlet + Voltmeter. Repainted Metallic Blue w/ new tank bages. Ear Shave (wo/ coasters) 40/140 NO shims 45MPG. MCCT conversion.

Planned modifications:
Custom LED turn signals. Windshield. Highway Pegs. (Possible) ignition adv. Tuxedo Mod. Ignition coil mod.

Last edited by Jason Pittenger; 05-03-2019 at 11:16 AM. Reason: spelling correction
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post #4 of 6 (permalink) Old 05-03-2019, 11:32 AM
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Quote:
Originally Posted by Jason Pittenger View Post
..
Plug reading is an art.
On this chart https://www.miniplane-usa.com/tips/sparkplugs.htm, I don't see a difference between 3rd row rightmost and 2nd from right 2nd row.
I'm not sure I could recognize a difference between 5th row leftmost and 1st row rightmost.
...
On your first example, one is ok and one is good, so no problem. 5th row left is blistered. Not real good pics either.

The symptoms you posted look like a lean transition between low and high rpm, depending where (rpm) you're getting the backfire. I'm thinking another shim, but I'm not where I can see for myself.

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post #5 of 6 (permalink) Old 05-03-2019, 11:43 AM
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I've considered doing something similar for tuning, though I'd be more likely to pursue it with a wideband sensor. Interested to see how this goes.

1986 VN750 27k miles
1999 EN500 32k
1983 GL650i in pieces. Someday it will ride again.
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post #6 of 6 (permalink) Old 05-03-2019, 01:50 PM
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the problem with adjusting the idle mix (air bleeds) is that it will only affect mixture at low throttle opening.. once you get to about 35% throttle (give or take), the main circuits have fully taken over, and thats changing jet territory

2005 VN750

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