Exhaust gas analyzer for tuning mixture

I've seen some of these older analyzers on ebay, as well as some newer handheld models for $100-$200 bucks online. Anyone have a specific model and use it? My bike runs well, and i've verified the valves are within spec, run propane around all joints to verify no leaks, and synced my carbs with gauges, but I have never been able to properly get a Colortune to work. I've had two early 80s Yamaha 4-cylinders, and I think i'm on my third Colortune, and at no point has any Colortune worked properly on either bike in the 15 years i've been tinkering with them. The bike seems to struggle idling with it in use, and if the Colortunes aren't sparking and causing the bike to miss, they simply show blue no matter if I turn them in or out. I'm a firm believer that they're a garbage product.

 

I've used a wide band in the tailpipe. It's OK for tuning idle mixture. Not going to tune the rest of the range with it, but that shouldn't be needed.

The thing is, you need to get the sensor into the exhaust stream somewhere before it's likely to have any ambient air mixing in. What I did was to buy a length of galvanized pipe from a hardware store, about two feet long, and then I drilled it and welded in an O2 bung so that it would be just at the end of the muffler, with the rest of the pipe sticking further back. This extra length of pipe keeps air from getting to the sensor, but also changes the resonance of the exhaust. At idle that shouldn't be a problem, though. The pipe certainly doesn't add any noticeable back-pressure.

You still need basically no gap where the pipe goes into the muffler, and the pipe should stick into the muffler a bit to further prevent induction of air into the pipe. I've used this successfully on a Kawasaki GPz 750 with a 4:1, and in stock exhaust, but with baffles removed, in a Ninja 250.

If you're going to be tuning a particular bike from time-to-time, it would be better to weld an O2 bung into the collector. They can be purchased with a plug so you can just seal the test port when it's not in use.

 

My header pipes are original, so they’ve got the little ports at the bottom where an EGA probe can be screwed in. Not sure how specific these ports are, and if you need to fabricate some sort of adapter when using anything other than the original Yamaha EGA.

 

I know this feed is a little old but I'm trying to find alternate ways to tune the carbs because I just can't seem to use a colortune very well. I'm curious about these O2 sensors. To get an accurate reading could you just remove the exhaust EXCEPT the headers and place the sensor on the bottom end of one of the headers (where it connects to the collector) and turn on the bike and start taking readings? I know it would be a little loud but who cares.

 

If your bike is a "YICS"" you should use the blanking tool to isolate each cylinder from each other.

 

if you have a digital tach, you can tune for max rpm without too much trouble.
these engines have valve overlap so a ega measures exhaust and scavenged a/f mixture

 

not needed.

 

the s tock exhaust has a port on each header pipe

 

I have all the parts of the system now. This photo shows the Innovate O2 sensor/meter, air pump and exhaust fitting (from Motion Pro). I just need some rubber tubing and an enclosure for the O2 meter with input and output air fittings. (and a box to put it all in). I'll probably try to reduce some of that wire length where possible. This innovate setup includes a control box that has serial output to connect to a laptop, which I don't need (at this point).

 

Then all you'll need is someone to steer your bike while you sit on the pillion watching the display, and looking over their shoulder at the throttle and tacho....

 

na, I'm going to thread the small brass tube into the down-pipe bung and test on the center stand.

 

When you are ready, let me know. Maybe I can lend a hand or at least watch!

 

Thanks, I plan to get on CAD later and design up a little bracket to mount the air pump that I can 3d print. Then, design the "test chamber" that the air lines and O2 sensor connect to. Wishing I had a lathe and a mill! I'll 3d print for a prototype, but I assume the heat of the O2 sensor may be too much for the plastic.

 

Well you'll only learn about the idle and progression circuits that way, even buzzing it the needle and main jet will only just be coming on.

 

Hmmm.....I'm pretty sure the engine can run up to redline while on the center stand. It won't be under load, but he'll get a good ballpark refrence.

 

That raises an interesting point. Since this Innovate gauge can do data logging, can I also capture RPM and then correlate engine speed and AF ratio... I'll have to look into that. First, get the thing to work, then worry about a case, then worry about logging and other inputs.

 

Sure it will but the needle will barely be lifted, due to the little air needed for this at no load - and just as importantly, this is a useless part of the speed/load "map", only seen if you buzz the motor on the stand. Hardly any point to it once past 4000 rpm or so.
Datalogging - now this IS useful - but you need an rpm and ideally throttle position to make it useful.

 

Yes you can, but you will likely need a pair of diodes connected to the coil negatives, and it will read double the rpm.
Can you also rig up a potentiometer onto the throttle spindle? OR, a lot easier, a map sensor teed into the petcock feed (or any of the other vacuum ports). You can find one of these at a breaker, 0 to 5V output usually.

 

looks good. It's a little more sophisticated then what I'm trying to do but I'll be interested in what you come up with and compare results.

 

you'll be half way to FI when this is over