Topic: o2 sensor to tune carbs?

[Nayl]

So there's a '77 750f for sale on my local craigslist - https://buffalo.craigslist.org/mcy/6013106405.html

What caught my attention is this: "Carbs jetted using wideband oxygen sensor (bung has been welded into exhaust collector for this)"

Has anyone done this?  I get the general idea, but it seems like a lot of unneccesary complexity.

[firebane]

It's actually the best way to do a tune. People do plug chops cause it's fast and easy

[70CB750]

I guess he is reading the voltage output while tuning carburetors.  Interesting, but would dynoing the motor be easier?

[firebane]

I guess he is reading the voltage output while tuning carburetors.  Interesting, but would dynoing the motor be easier?

Dyno doesn't show you how things are running. A wideband shows you your a/f ratio properly so you can see where your bike is running at various throttle positions when riding.

[70CB750]

You can use exhaust analyzer with dyno.

[madmtnmotors]

I intend to build my own:

http://www.buckeyetriumphs.org/technical/Carbs/AFMonitor/AFMonitor.htm

[flybox1]

The o2 sensor is not a selling point.
He installed ONE sensor, at the collector when there are 4 carbs to individually tune? 
Point being he can have one carb lean and another rich, and STILL have a good A/F reading when gasses from all four are mixed and being read. 

[madmtnmotors]

The o2 sensor is not a selling point.
He installed ONE sensor, at the collector when there are 4 carbs to individually tune? 
Point being he can have one carb lean and another rich, and STILL have a good A/F reading when gasses from all four are mixed and being read. 

I intend to build four of these.

I intend to build my own:

http://www.buckeyetriumphs.org/technical/Carbs/AFMonitor/AFMonitor.htm

A set of Mac headers will be used for setting up the street bike with bungs near the bottom of the down tubes. The track bike will have bungs permanently in place and plugged when racing. The street bike testing header will get it close and if a similar (or same) header is used for everyday riding then your done. Four into four would only require one "sniffer" inserted into each tail pipe at a time. If the four into one is significantly different than the test pipe then at least the initial set up with the test pipe would get you even across all four and then the "sniff test" from the single tailpipe would let you know how much to adjust all four carbs evenly. Some variations may be present if the everyday header is a lot different than the test header, but hey, compromises have to be made... 

You could build just one and measure each downtube one at a time, recording your results as you go, but that sounds like a lot of work.

[flybox1]

Nice.  Keep us posted on how it works.
Correct.... for a 4:1 exhaust setup you'd need sniffers in each header to accurately measure A/F, and adjust each carb as needed.
Ideally, you have a 4:4 exhaust, and can measure each at the pipe

[PeWe]

If carbs are correctly jetted it does not matter how that was done. An air fuel gauge permanently mounted is an option to claim money for.

I have a Daytone Wego III to verify my carbs  during normal driving
http://www.daytona-sensors.com/wego--iii---wego--iv---single-channel-displays.html
. It is different on the Dyno and full throttle. The carbs can be way too lean and still give good power at full throttle. If the pilot circuit is too lean, engine will run very hot in normal cruising speed like up to 120kmh on 5:th gear.  Throttles opened just a lttle
I know, the dyno showed not too lean but some valves were almost white when I inspected the valves. Plugs had already showed too lean.

I'll run each cyl separate since I have 4-4. I need an exhaust sniffer. A 20 cm long pipe to put in the rear. That pipe with the sensor. cabling forward to the unit. The af ratio seen as number while driving and logged with rpm as reference.

I'll use an action cam that will show everything, speed, rpm and air fuel ratio.

There is another smaller unit. No logging but visible anyway. A camera can be used too.
https://www.rbracing-rsr.com/rsrgauge.htm

It is better when all cyl can be checked. A permanent mounted sensor in the 4-1 might not show an individual cyl with carb leak.

[sinister902]

almost all 4cyl cars use two oxygen sensors, and they aren't even wideband (not nearly as accurate as a wideband) and they put one in the collector BEFORE teh catalytic converter and one AFTER the catalytic converter. All dyno tuning shops use a single wideband oxygen sensor in a sniffer tube inserted down the muffler to do the same thing as what's described in the ad....to verify ACTUAL air fuel mixture more accurately than inspecting spark plug chop results by eye. What the ad is saying, is that rather than just looking at plugs and throwing jets in the bike until it rides OK, it was further adjusted using a sensor to make sure mixture was as optimal as possible.

J.webster designs has a nice sniffer kit and does this. As do I after adjusting jet sizes the traditional way (plug chops). It's merely an EXTRA measure. using a bung in the actual exhaust is also more accurate than a sniffer tube, for what it's worth.

[flybox1]

Sinister....Yes, but WHICH carb do you adjust is my point, when gasses from all four are being collected and then tested?
If you want to go the extra time and expense to be accurate, dont be a lazy@ss and put in just one on a 4:1 system.
The ads selling point (and added $) that is has been 'tuned' because it has one installed does not fly with me.
Just sayin' 

[sinister902]

Sinister....Yes, but WHICH carb do you adjust is my point, when gasses from all four are being collected and then tested?
If you want to go the extra time and expense to be accurate, dont be a lazy@ss and put in just one on a 4:1 system.
The ads selling point (and added $) that is has been 'tuned' because it has one installed does not fly with me.
Just sayin' 

that's making an assumption that in addition to the o2 sensor nothing else was done/considered.

anyone competent in carbs knows to check for leaks, vacuum sync, and check plug colors in addition to using a sensor if one is used...... pretty easy to contact seller and simply ask these things instead of us all on this thread throwing around unknowns.

tuners still don't install a separate bung per header to tune a bike when you take your bike to a dyno tuner.

[PeWe]

Plug will not show the whole thruth either. Floading floats cause way too rich at low and will soot the plugs. If pilot circuit (air jet included) is way too lean it might not burn the soot away quick enough. Plugs will not show the lean status. The sensor however will show the actual mixture.

I have some plugs that look as black velvet but carbs were way too lean later on....Oil temp was very high (230F/110C), but plugs were really dark.

More about Lambda vs wideband sensors. http://www.aa1car.com/library/wraf.htm
EDIT: forgot this link for more to read https://www.enginebasics.com/EFI%20Tuning/AF%20Ratio%20Basics.html

[flybox1]

tuners still don't install a separate bung per header to tune a bike when you take your bike to a dyno tuner.

....when its computer controlled FI  Yes, you only need one sniffer.   But we are dealing with 4 individual carbs here.  They need to be treated that way.
A bung at the collector on a 4:1 (non FI) system does not tell you which carb is off, or if when the AF is right, that all four carbs are right.
You could still have improper mixture between carbs where the sum of the gasses at the collector equals proper overall mixture.
One collector bung on a non FI bike gives incomplete, inaccurate data.

[Duanob]

Plug chops just seems way easier and cheaper at this point.  At least you know wwhich carb needs adjusting. Especially if you don't need an emissions test.

[PeWe]

Plug chops just seems way easier and cheaper at this point.  At least you know wwhich carb needs adjusting. Especially if you don't need an emissions test.

Yes, but it can trick you. At least me. I had a long period of tuning that started with floading floats, advancer that kicked in way too early (sloppy springs) and finally one ¤%&(#"# NEW Dynatek graphite wire with intermittent function that made the bike to react and sound as too lean or too rich.
Plugs were mostly way too dark and oil temp way too high.
I changed all jets (not needles, except position, tried them all) several times and noted all jets with comments in an excel file and scratched my head...

Edit: I understand (learned the hard way) after that trip why the experienced guys recommends to check float levels as first step.
(ignition with correct full advance rpm too)
Then continue with pilot circuit with the pilot jet, air/fuel screw. Air jet should be OK (maybe if needles does not help)
Needles, and main jet. It helps if others have done it before with good result.

With a sensor the result will be reported direct and you can note the exact throttle lift. Quciker to find the "perfect setting". Struggling with carb jetting can ruin the riding season. Invest in an AF gauge is then well worth it. Avoid melted pistons is also nice

[sinister902]

tuners still don't install a separate bung per header to tune a bike when you take your bike to a dyno tuner.

....when its computer controlled FI  Yes, you only need one sniffer.   But we are dealing with 4 individual carbs here.  They need to be treated that way.
A bung at the collector on a 4:1 (non FI) system does not tell you which carb is off, or if when the AF is right, that all four carbs are right.
You could still have improper mixture between carbs where the sum of the gasses at the collector equals proper overall mixture.
One collector bung on a non FI bike gives incomplete, inaccurate data.

modern sportbikes are in fact EFI, but there's still 4 individual throttle bodies each with it's own injector on a 4cyl sportbike. I fail to see the difference in use of a sensor vs 4 carbs. what if one injector is partially clogged running that cylinder lean while you tune the bike rich enough that the other three are compensating by the time the gauge reads the mixture at the collector?

My point is you're still arguing one bullet point out of tuning carbs pretending the checks and balances were not done by whomever did the tuning. listing that a sensor was used to aid in carb tuning does not necessarily mean that it was the ONLY thing used to decide jetting and settings. Every point you've made could be argued equally for an EFI bike with more than one cylinder.

again, there's lots of variables in carb tuning which I'm not arguing against. If someone said they did plug chops to jet their carbs that would be just as easy to come in here with all the hypothetical situations that may arise skewing results but that doesn't make any one way of "tuning" carbs better than another. to be done "right" as has been discussed in this thread floats must be checked, seals must be checked, boots must be checked, etc.....the list goes on. but that's not what the question was. The question was can an oxygen sensor be used in the process of jetting a carb and the answer is yes. Just because it can be doesn't mean it needs to be, nor does it determine if it was done right or wrong.....but again, that's not what the thread was about to begin with.

again, the PO should ask the right questions if interested in the specific bike in the ad....and should go see/hear it run/ride for himself to determine if there's any issues. If nothing else at least it wasn't just left alone with stock jetting on aftermarket filters and muffler.

[evanphi]

Only question I have is: did he use a wideband alignment tool to install the checked tape crooked on the bikini fairing? 

+3.68 HP.

[hudstr]

If I remember correctly, the bike was listed around $2500, well now it popped back up again, this time in Rochester instead of Buffalo. Now they want $4500, so someone is in for a rude awakening when no one will buy it. Also adding "Rare" to the title means you can add on another $1000

https://rochester.craigslist.org/mcy/6161216299.html

[SOHC4 Cafe Racer Fan]

Ah. the number 33 bike.  Now I remember what it looks like.

Frode2 has a wideband AF sensor for his CB with a billet JMR 1000cc cylinder beastie:
http://forums.sohc4.net/index.php/topic,163983.0.html

[sinister902]

guy in rochester bought it, rode it for the season, and is trying to double his money.

[PeWe]

The Dyno run guys use A/F sensor to tune the engine. Very often 4-1 pipes and only one sensor sticked into the exhaust.

It would be nice to have a sensor for each cylinder permanenty mounted to supervise how the engine run and avoid meltdowns, getting good power and fuel economy. Multi colored LED for each. Carbs will become dirty or get leaks and suddenly deliver lean mixture. I have been busy with other things and not tested my Daytona Wego III yet. It need a sniffer pipe. I'll run each pipe, one by one.

Time to develop much smaller sensors, like an M6 bolt, 15mm long, max.