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Where's Max?
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The lean condition on my bike has got to go. The engine and exaust are all stock yet the bike continues to be lean. The dealership has already updated the ecu but it didn't do anything. Within the next 2 weeks I will be getting a 5-gas analyzer on it. Don't have access to a dyno, so just going to use the sniffer. This raises my questions.

At what RPM should I be using the 5-gas analyzer to get the AFR?

I've read that the AFR should be about 13.8:1, is this correct?

Assuming it's going to tell me what I already know, what is the cheapest way to correct this problem?

The choices that I've examined: PCIII, SERT, VFRI-D. I know there are several others out there, If I were to install something other than the SERT or VFRI-D, I would want something very inexpensive that works reliably.

Questions? Comments? Answeres prefered. Thanks in advance!
 

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VRF0RUMS ORIGINAL
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5,763 Posts
Xoygeha said:
The choices that I've examined: PCIII, SERT, VFRI-D. I know there are several others out there, If I were to install something other than the SERT or VFRI-D, I would want something very inexpensive that works reliably.

Questions? Comments? Answeres prefered. Thanks in advance!
I only have experience with the PCIIIusb. They have a good Stock map that will take care of the lean condition from the factory. Easy install IMHO. Although not inexpensive the PCIII is easy to program (load maps) and adjust.
 

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THE DORK-ROD
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344 Posts
My D model was very lean from the factory.I went with the H.D. race fueler, costs only 180.00 and was able to correct all lean conditions.:moped:
 

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SNAFU
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13,094 Posts
Street Rods as well as D's seem to run a bit lean from the factory but going though all your efforts to correct what is probably a minor lean issue seems a but obsessive.

There are hundreds of target AFR's in the ECM, picking a number at a specific RPM / Throttle Position is pretty much impossible expecially considering a 5 gas will require you to hold a specific RPM/TPS for a few seconds at a time to log a reading. You are going to go through a ton of effort and you'll end up at best marginal results. The range of target AFR's is from 12.0:1 to 15.0:1 so there really isn't a target you can home in on. 13.8:1 would be a bit rich for cruise (part throttle) but too lean if you go above 75% throttle. Good luck.

With no modifications to the bike your best thing you could do would be to use a Race Fueler or TFI and trim a bit more fuel into the areas you feel are lean. Many who have been dissatisfied with the EPA lean condition from the factory have done this and are very happy. Don't waste your time on PCIII's, Race Tuners or VRFID's, that's MASSIVE overkill for you situation. I also wouldn't waste my time 5 gas analyzers unless you simply want to play with one.
 

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My stock Night Rod runs lean. After a 130mph plus run, the pipe tips were almost white instead of med. grey. I installed a 5K OHM potentiometer in series with the thermistor on the airbox. During my first ride of the day, when the lean condition was the worst, I turned the pot higher until the stumbling went away. Does anybody see why this wouldn't be a sollution?
 

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mrbuell said:
My stock Night Rod runs lean. After a 130mph plus run, the pipe tips were almost white instead of med. grey. I installed a 5K OHM potentiometer in series with the thermistor on the airbox. During my first ride of the day, when the lean condition was the worst, I turned the pot higher until the stumbling went away. Does anybody see why this wouldn't be a sollution?
I see no issue other than the solution may be too global, and of course is unidirectional, in that it can only richen the AFR, buy making the ECM "think" the intake air is cooler than it really is.

Clearly all the simple pulse stretcher type fuel management systems are also unidirectional but they do have some control over at what RPMs the AFR is richened.
 
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