Oxygen Sensors. morphed Choke Removal Thread

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bpatton

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Has anyone got any experience tuning four strokes with an Oxygen Sensor? I have an old header that I could braze a bung onto for a sensor. I'm using a single Mikuni, so it should be sufficient. If I got the right sensor and meter setup and was able to get some reliable data I'd go ahead and do it. I might even be able to actually learn what correct jetting sounds and feels like. So then I could amaze my friends by saying, "That sounds kinda fat there on yer mains." As it is, I'm clueless. Pilot, cutaway, needle, and mains; I think you could work it out without a dyno. All you'd need is a wide open road.

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I'll have to dig around and see if I can find it... It being a very simple project plans (I made one) a 10 LED bar readout made from cheap parts purchased at radio shack and any 3 wire O2 sensor (3 wire is heated)...

You weld in a bung for the sensor and feed it 12 volts... 5 LEDs is ideal, less is lean, more is rich.

or you can buy something like this:
broken link removed


ETA: I found it... Build your own if you like to tinker... broken link removed
 
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You might ask Jim what he uses for his FI. It might just be a static map. Or maybe not.
 
I use a gas analyzer on the dyno and a wideband 02 sensor on the road for tuning my FI bike.
You must keep in mind that there are two common types of 02 sensor. The narrowband sensor as used on most cars is a simple 1 to 4 wire heated or unheated sensor that is acurate only at the stoic fuel mixture of 14.7 to one. Above or below that mixture you will have a reading but it will not be accurate. It was designed for cars with simple catalytic convertor systems which only are efficiant when the mixture is at stoic. A Norton engine or most any air-cooled motor can not be orperated at stoic when under load or it will melt down. Best idle mixture is usually around 13.5 to 1 and around 12 to 1 under load.
The second type is the wideband sensor. It must be used with it's matched controller which provides temperature regulation and calibration for the sensor. It can give an accurate reading from around 9 to 1 to 22 to one. It is the one to use for getting readings under load. Inovate Motorsports makes a popular unit.
An 02 sensor reading is not an absolute due to the fact that camshaft overlap will influence the reading due to oxygen and unburned fuel getting into the exhaust system during the overlap period. An exhaust system must be sealed as even a small leak will throw the readings way off. The o2 sensor will need to be at least 24 inches from the end of the muffler or oxygen flowing in from the outlet will mess up the reading. Readings taken with an 02 sensor should be weighed with plug readings and common sense. Once you know what readings give the best results with the engine you are working on then they are a good tool to use for camparison. Jim
 
I purchased a wideband o2 sensor and reader, now I'm shocked and slightly concerned.
73 850
boyer
34 vm mikuni #3 slide,159 p2,6dh4 needle, 240 main, which are pretty standard settings from what I can gather.

I fitted the gauge and checked the hot idle settings, about 13.6 about what Jim suggested, went for a ride,every thing else up to the main jet was low 10's, way to rich, on the main jet it was at 12.5, I tried a 260 and it went down to 10.2 and wouldn't pull, so I believe the gauge.
I left the main jet at 240,changed to a P0 needle jet and dropped the needle a notch, I had to file a slide to get that leaner , it may be a #3.5 but more than likly a #4 as it is 1mm deeper than the #3. Went for another ride ,idle 13.6,60-70mph no load cruise 13.2, above 70 under power it goes from mid 11's to low 12s on the needle then back to12.5 on the main

Now the question is does that seem correct, or has any one coughed up to get their mikuni properly dyno tuned with similar results?
My worry is that I thought my bike ran allright before and it definatly runs hotter now, I know I need to do a plug chop, checked them when I got home and their was no ball of aluminium on then so thats a +
If this is how they all are it's no wonder they foul plugs on the choke quickly.

My next thread will probably be on how to remove melted piston from bores :shock: :shock:
 
bpatton said:
...I have an old header that I could braze a bung onto for a sensor...
Click to expand...

That's going to give you different results & readings than the pipes you will be running regularly, I would think...
 
bpatton said:
Has anyone got any experience tuning four strokes with an Oxygen Sensor? I have an old header that I could braze a bung onto for a sensor. I'm using a single Mikuni, so it should be sufficient. If I got the right sensor and meter setup and was able to get some reliable data I'd go ahead and do it. I might even be able to actually learn what correct jetting sounds and feels like. So then I could amaze my friends by saying, "That sounds kinda fat there on yer mains." As it is, I'm clueless. Pilot, cutaway, needle, and mains; I think you could work it out without a dyno. All you'd need is a wide open road.

.
Click to expand...
Carburation and air cooled engins /////Would a oxy sensor suggest a spot on mix...15/1 ...approx? I would strongly recommend a slightly richer mix...i try for a "nice brown" on a correct heat grade plug,,,swiftly moving on...the old colour tunes are good....and boy do they show up the limitations of carbs! Gas ring BLUE!!!!!!!! then your are cooking my son!!!
 
john robert bould said:
Carburation and air cooled engins /////Would a oxy sensor suggest a spot on mix...15/1 ...approx? I would strongly recommend a slightly richer mix
Click to expand...

With every thing else correct ,timing ,no ex leaks, it seems to be telling me whats happenning, but it's the lack of experiance and the air cooled motor factor that keeps making me err on the rich side,I'm trying to set around 12-1 , but it's all a learning curve and they still make pistons.
 
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