Exhaust gas analyzer/carb adjustment.

[Robert]

Anyone besides me used a gas analyzer to adjust their carbs. I bought a used exhaust gas analyzer from a shop that was going out of business, I always wanted one but was not willing to shell out 3 to 5k to get one. So when this came up with some other equipment I got it. When I started to use it what I noticed was one bank of carbs were good the other was a bit rich. I had started at the usual 1.5 turns out because I have the 38 slow jets, at the time I did the carbs some months back. Since then I played with the mixture a bit looking for the best adjustment but it always seemed base adjustment was the best. What I found when I used the analyzer I had to lean out one bank a bit and got the mix pretty good. What I noticed was improved throttle response and transition from idle to acceleration or anything off idle. I was kind of surprised at the quicker response and smoother cruising  and that idle didn't change all that much. I did not expect this and wondered if anyone else has tried to adjust their carbs using a exhaust gas analyzer. I know that some dynos have analyzers on them but wondered about anyone elses experience at carb adjustment this way.

[Tx Bohemian]

Way back in my car mechanic-ing days the shop I worked at bought a scope with an exhaust analyzer (we're talking in the late 70s) and I thought it was the bees-knees!!
You could really get the carbs adjusted just right, better than tach and sound.

I always thought the 1-1/2 or 2-1/4 method we all do on these bikes was just a close "estimate", ok- but could be better (old car mechaniking habits).

[Attic Rat]

I have been using a digital fuel air ratio meter for several years, I have an exhaust system with two o2 sensors mounted in them. That way I can take live readings on both sides at one time. I also built a probe to probe the exhaust. Let me tell you there is a difference between readings at the header than at the end of the exhaust

[John Schmidt]

Robert, I'd love to see that setup. Makes me curious now. The old girl runs pretty good as is, but one can't help but wonder if it can be improved....especially the MPG. If I could only control that right wrist.... 

[Robert]

Here ya go John not much to look at but its front and back shots. The front has all the digital displays HC,CO,O2,RPM, buttons and such but the the reason for the back shot was the hose end and the calibration gas tank along with the filter and back panel. I am pretty happy I have it, but they are pretty sensitive and costly to repair. With the switch to o2 sensors like Attic Rat has done these machines are not so much in demand. O2 sensors though also have their particular problems and dont give as much info as this machine does.  Unless you go to the new 4 wire digital type but then you still need a computer to read them. One thing nice about these machines is you can tell if you have a vacum leak that is letting air in when you learn the numbers.

[John Schmidt]

I'm curious though, how do you know which cylinder to adjust? If you have the 6x6 pipes that would be easy, but the stockers???

[Robert]

First look at the numbers and see where they are high or low or about 2% hc would be good. Then go and pic a carb adjust it and see where the numbers go if they go up then you know your going the wrong way. If they go down then adjust it to the closest reading you want to be at then proceed to another. I have 3 into 1 not hard to adjust, no matter how many you have its all the same principle. The readings change fast so its not guess work which way you are adjusting them or a cylinder that is off. Have a miss in one cylinder and the numbers go through the roof fast. Then you will never really get a good read unless you go cylinder by cylinder. But in the analyzing of the readings it is the first step to steering you to the cause of the problem. Air leaks, bad engine or any other related issue will stop the readings from being where you want them either lean or rich and the mix and amount of the gases will tell you a area to look at. High o2 vacuum leak, high hc, to much fuel. One point I want to make is it is a average of the gases out the exhaust so one cylinder will not dominate the readings so much so as not to have a change when adjusting other carbs. So if one cylinder is at 4% hc and you adjust the wrong cylinder there will be some change. So it may drop down to 2.5% or 3% and you get it the lowest you can and it will usually be good to go and no need to readjust is usually necessary.

[Ricky-D]

Behind the exhaust pipe covers you can find the individual pipe coming from each cylinder.

It wouldn't be too difficult to access the exhaust gasses with a port in each pipe.

Simple enough to close off the ports depending on the method used to gain access.

The cover would hide the work.

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[97BLKVALK]

Robert,

You should bring to Inzane and recoup your investment and make a couple bucks, it looks like there would be enough interest.   

Michael