O2 Sensor Location

[Guest]

Hi all,

I'm looking to put a O2 sensor on my GS750 to help me dial in the carburetors. My question here is where do most of you put yours at? I have an unknown brand 4-into-1 on my bike and the collector area seems to close to the oil pan to mount the sensor in the proper orientation. (I think) the sensor needs to be pointed down to avoid water/moisture from getting into the sensor when the bike is parked. I have plenty of space on my slip-on muffler, just downstream of the collector but I do not know if the slip joint will throw off the readings at all. Also has anyone had any experience with the tailpipe mounted sensors? I may be going to a different exhaust in the coming months and that would save me from having to have a bung welded twice.

While I'm at it where is the best place to mount a gauge/logger?

Thanks

 

[Steve]

My question here is where do most of you put yours at?

From what I have seen over the years, there might have been 8 or 10 guys here that have done that, so, considering that there are hundreds (thousands?) that use this board regularly, "most of us" don't even have one. Good luck in your quest. :encouragement:

.

 

[steve murdoch]

You need to talk to Chuck78.
http://www.thegsresources.com/_foru...AFR-gauge-for-carb-tuning-on-modified-engines

 

[ArttuH]

It doesn't need point exactly downwards. Anything between 9 and 3 o'clock should be fine. It would be good to get it as far as possible from tailpipe exit. Otherwise there might be reversing fresh air getting to sensor at low revs.

 

[posplayr]

Tail Pipe sniffer. I used about 30" of copper tubing to go from can to in front of the 4:1 collector to avoid any air leaks.

I welded the bung into a piece of 1" iron plumbing pipe

 

[Guest]

You need to talk to Chuck78.
http://www.thegsresources.com/_foru...AFR-gauge-for-carb-tuning-on-modified-engines

Ah Chuck seems to know everything!

From what I've heard/read I think I'm going to have bung welded in the slip on muffler just downstream of the slip on connection. If that doesn't seem to produce reliable results I'll take the exhaust off and weld it into the collector instead. I think I may be changing the muffler soon, after looking at mine I can't believe how restrictive it is; the bike isn't very quiet either. Will update with results

 

[thebrandonbeezy]

I was gonna say just use a sniffer

 

[posplayr]

I was gonna say just use a sniffer

I already posted that; did not penetrate.

 

[hannibal]

Tail Pipe sniffer. I used about 30" of copper tubing to go from can to in front of the 4:1 collector to avoid any air leaks.

I welded the bung into a piece of 1" iron plumbing pipe

Would you please explain your setup more? Or maybe a pic? I don't understand tailpipe sniffer with the tubing and 1 inch bung.

 

[posplayr]

Would you please explain your setup more? Or maybe a pic? I don't understand tailpipe sniffer with the tubing and 1 inch bung.

You used to be able to buy the "T" from Innovate sports. It was probably $100 back in 2010 when I did this.

https://www.innovatemotorsports.com/xcart/home.php

The 30" copper tube is extending up past the collector. The exhaust flows straight through the "T" and comes out through the piece of rubber hose. There is a short heat shield to stop it from melting.

 

[Chuck78]

The innovate brand tailpipe sniffer camp-on mount isn't as accurate, it gives a slight delayed response, and only works on very large i.d. baffles, and dies not like single cylinder exhausts at all. For single cylinder applications, the bung must be welded into the mid pipe. Same may go for 4 into 2 dual exhausts afaik.

I welded my o2 bung ($6.99 from Jeg's with a plug for after tuning is completed) into the end of the mid pipe or beginning of the muffler where the center stand area is.

Keep the mixture around or richer than 13:1 if you have higher compression pistons. This helps run cooler, and fights off detonation.

 

[Guest]

For those wondering, here's what my setup has become:

I decided to go ahead and weld the bung into the muffler about 2 inches behind the slip joint. I talked to the tech line at innovate motorsports and they told me any error there should be insignificant and that if anything, it will error by reading leaner than the actual mixture so there should be a safe margin there. I thought it would look horrible just sticking out of the muffler but it doesn't look to bad after all.

A couple unexpected things to note about the sensor install is that even with a pretty stout factory charging system my innovate motorsports gauge will shut off and give a low voltage error at redlights with the headlight on. I'm currently installing a relay straight to the battery to help alleviate the problem. This isn't much of an issue except for the fact that the heater comes on for 30 seconds or so every time I come to a stop. I figure this can't be good for the sensors longevity so I will remove it and install a plug when I get done tuning. On the plus side, as far as I know the gauge's low voltage warning takes precedence over all other warning so even with the sensor uninstalled it may function as a charging indicator.

I'll also mention my tune here in case it can help anyone,

The bike is a 1978 GS750 that is stock for the most part. It has a 4 into 1, UNI replacement filter and I have a larger rear sprocket.
Here's what I've come up with:

Main: 102.5
Pilot: 15
Idle fuel screws: just under 1 turn put
Air screws: About 1.5 - 1.8 turns
Needle: 3rd position from bottom
Factory float height

This setup leaves me with an idle AFR of about 12.4, cruises at 60-70 at about 14.8 and as I roll into full throttle it jumps to the high 11's and leans out as the RPM increases to low 13's. This is a little leaner than I would like and as a result I've started running 89 Octane non ethanol to see if it will bring the mixture slightly more to the rich side. If I were to do some long distance high speed cruising or at a track I would probably go up a main jet size or 2 but for the type of riding I do this seems to give the best response and decent fuel economy. Last thing to note is that on my carbs they seem to go very lean and small throttle openings. Just barely above idle results in a AFR of near 17. I can feel this when I'm riding but haven't been able to correct it yet.

 

[Guest]

Here's where I mounted the gauge, I decided not to use the headlight dimming feature and the lights don't seem too bright at night

 

[Chuck78]

I drilled my pipe near the center stand for my weld-in bung, so that the o2 sensor sticks out where the center stand would have been. It's completely concealed in this location aside from the sendoe to gauge/power wires dangling around my bike held on with zip ties.

your bike sounds a bit too lean for my comfort, it's air cooled, and you're running water cooled AFR's, and slightly on the lean side even for water cooled. Running 89 or even 93 octane won't make it run any more rich. It will just resist detonation more under normal conditions. Too lean is not a normal condition.

What's the outdoor temperature and humidity when you are getting those readings? Perhaps when it gets more humid and warmer, it will richen up?


When testing the main jet size, are you drag racing it through the gears and revving it up to 9500rpm or so at WIDE OPEN THROTTLE? Main jet ballpark sizing doesn't come into play much at all until about 60% throttle.
it helps to mark the throttle grip and handlebar control housing with tape and marker to note throttle positions

 

[Guest]

I drilled my pipe near the center stand for my weld-in bung, so that the o2 sensor sticks out where the center stand would have been. It's completely concealed in this location aside from the sendoe to gauge/power wires dangling around my bike held on with zip ties.

your bike sounds a bit too lean for my comfort, it's air cooled, and you're running water cooled AFR's, and slightly on the lean side even for water cooled. Running 89 or even 93 octane won't make it run any more rich. It will just resist detonation more under normal conditions. Too lean is not a normal condition.

What's the outdoor temperature and humidity when you are getting those readings? Perhaps when it gets more humid and warmer, it will richen up?

On my exhaust the muffler joint is right in front of the rear tire and the muffler hangs out to the side just enough to prevent me from putting the sensor in your location.

As for the AFR's, I had assumed just like a water cooled engine that under light load while cruising I shouldn't have a problem running mid 14's. Most water cooled engines run mid 15's when cruising with no problem. As soon as I go to full throttle it drops to mid to low 11's and then climbs just barely reaching over 13 at redline. Most of the rev range is not over the low-mid 12 mark. I'm in Florida and it has been very cold lately while I'm tuning (low 40's about 60% humidity). I just made a guess that the non-ethanol fuel may run slightly richer because from my understanding the guys that run E85 have to run bigger jets for the same AFR's. It may just be an insignificant difference though.

When I first installed the sensor it was reading very rich everywhere except full throttle. A 60 MPH cruise resulted in a high 10 low 11. I left the mains alone and dropped the needles one clip. I re-adjusted the air screws and fuel screws but thats about all I've changed so far.

 

[hannibal]

Thanks for the pic and explanation Posplayr.