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Surprising AFR numbers on 2t

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I just finished putting the pipe back on. I welded a bung about 21 inches from the head. Where I thought I was rich, it is showing lean, especially for a 2t. I have done this many times with a 4t but this is my first 2t. Hearing that others have said it will not work on a 2T, LOL, I have to prove it to myself. I never could find anywhere on the net as to where my AFR numbers should be that seemed to come from experience. I shoot for 12.8 to 13.2 throughout the entire throttle range with a 4T. I have seen that a 2t needs lower, 11.5 was the average of what I found. But on my 2T today, I was getting 14 on the low side and 16 on the high side. To lean even for a 4T. But I was so confident that I was rich. I run richer jets than most all of this model owners. My temps stay extremely low, fan not coming on often. My piston wash looks good. I have not done a plug chop. The AFR numbers were consistent with what I was doing with the throttle. Predictable, stable. So I feel like I was getting a usable reading inspite of others saying it will not work. So I wonder, does the fuel/air meter need to be recalculated for a 2T.? Is it possible that it is this lean? Or is it reading leaner than it is, the reason others say it will not work? Input wanted

Edited by 1gr8bldr

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12 minutes ago, William1 said:

Sensors get trashed quickly in a 2S.

Yea, I have heard. This is my second one already. I heard that being rich is tough on them.?

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8 minutes ago, 1gr8bldr said:

Yea, I have heard. This is my second one already. I heard that being rich is tough on them.?

Not being rich, the oil in the exhaust screws up the sensor. Sort of like how leaded fuel in a car with catalyst converters gets teh converters ruined, the lead cots the catalyst, preventing it from functioning. Most 2S guys use EGT, which is hard to do on a bike as the rpms varm. A sled or  boat, the rpms tend to be much more steady and therefore an accurate egt read. My suggestion is to not be so concerned about AFR and perfect tuning unless you are the wrench for a top tier pro team. Otherwise, you will spend all your time and money and really have little to show for it.

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Just in from changing out jets. LOL, soaking wet. I had to warm up the bike in the rain. Originally the bike had 122/42new . I changed to 125/42 to help with the hanging rpm's. That gave the lean readings of 14 to 16 on the idle and main. I changed to 128/45 and moved everything to good numbers... if it were a 4t, 12.8 to high 13's, the main being closer than the idle circuit. I adjusted the air screw to bring the numbers down even more but it would hardly run as if it were on choke. But strong, crisp, where it is now. I will play with it more to verify, just not in the rain. I hate that these carbs don't have a bowl drain screw. Float height is not that critical and I use the clear tube method with other carbs. It can be jetted to run perfect hi or low but when comparing others jetting to your own there has to be a standard baseline otherwise it's a moving goal post. My bike was running so good, I feel stupid changing things, but if it were really 14 to 16, that's to lean. Motor life would be cut way down..... yet my temps were always low and fan seldom came on?????

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2 hours ago, William1 said:

Not being rich, the oil in the exhaust screws up the sensor. Sort of like how leaded fuel in a car with catalyst converters gets teh converters ruined, the lead cots the catalyst, preventing it from functioning. Most 2S guys use EGT, which is hard to do on a bike as the rpms varm. A sled or  boat, the rpms tend to be much more steady and therefore an accurate egt read. My suggestion is to not be so concerned about AFR and perfect tuning unless you are the wrench for a top tier pro team. Otherwise, you will spend all your time and money and really have little to show for it.

I can dial in a 4t perfect within an hour, assuming it does not need a different needle taper, so it's not much trouble. LOL much better than the timed runs I used to do to find the best main. But the 2T, I don't know. This bike is known to have hanging rpm's, lean run away and stuttering. So if it were not for trying to figure this out, I would just rough tune and ride. LOL, my riding skills are more in need than my wrenching skills. But if I eliminate all three issues with the sensor, without having to buy 3 sensors, I will be happy.... and have learned something

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2 hours ago, William1 said:

Not being rich, the oil in the exhaust screws up the sensor. Sort of like how leaded fuel in a car with catalyst converters gets teh converters ruined, the lead cots the catalyst, preventing it from functioning. Most 2S guys use EGT, which is hard to do on a bike as the rpms varm. A sled or  boat, the rpms tend to be much more steady and therefore an accurate egt read. My suggestion is to not be so concerned about AFR and perfect tuning unless you are the wrench for a top tier pro team. Otherwise, you will spend all your time and money and really have little to show for it.

I assumed rich was also a culprit, maybe not? I was playing with ufo's, homemade, getting so much more power but I could not overcome that rich idle that ufo's create. I did eventually by cutting the slide but then I would get a lean bog at the fast crack of the throttle. I assumed my first sensor went bad because of the rich idle I was inflicting on it. 

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1 hour ago, YZ144FirstTimer said:

this

Last time I googled it, I found several sources, of which said 11"s. This is the highest I have seen. This site shows what else can be done. But all that software, computer readout, etc, a waste of time, thought and money. It's way to simple to complicate it like that. No need for any of that. That would be like using a computer software to map out and record how to count to three. 

Edited by 1gr8bldr
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Yeah... the real way to tune is EGT and a brake dyno. Very few have access to that. Next best thing is EGT and a nice long medium hill that you can ride and repeat identically the runs, matching distance and recording times. A lot of effort for minimal return. With most 2S, I jet rich and slowly lean out to were plug fouling is no longer a issue. Might lose a Hp or so but in real life, that means nothing.

I use a Wideband once in a blue moon to confirm numbers. Again, unless you need to squeeze every bit of power out for a rider that can make use of it, being off by a whole point is not apparent to the typical rider. But testing and playing the numbers can be fun. Until it is not 😉

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I was once on the RZ350 board and a guy there used Megasquirt to EFI his bike. He mounted the sensor on the top (out of oil's way) and in the middle of the belly. If you mount it too close to the exhaust port I think it will show scewed readings because of the effect the pipe has at different rpms as it draws fresh mix out of the cylinder into the exhaust before cramming it back in.

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