It kind of cracks me up that this thread sounds like it could be something on a fitness forum as well.

Who's running or has run factory lean long term?

For my riding style, the 103 is sufficient in terms of power, especially having sat on touring bikes with the same engine. I never changed the air cleaner out, and then got to liking the football and the inserts that can be put on it. I'm running Python slips on stock headers, and I'm content with the look and sound.

Long story short, my bike hasn't been tuned or EFI remapped. At least for now, the only things I'll do to my bike are aesthetic. My bike is still running factory lean, and I just might leave it that way unless some advice compels me against that route. I want to leave it. The fuel efficiency is fair (~40mpg), the heat off the engine is tolerable even in the middle of the summer when it's 115, and I get synthetic fluids put in to tolerate the heat better and retain their viscosity.

Since factory lean running is hotter, I'd like to hear from anyone who ran in that condition for the long term. Both positive and negative (hopefully there aren't any) experiences are sought. Please share your mileage as well in your account.

PS - How much mileage should one expect to lose due to an EFI remap?

 

I ran an 04 Electra Glide with the stock AC and tune for 45000 miles with no mechanical issues. My current bike is an 09 Road King and it is running the stock AC and tune as well, no problems in the 2 years I have owned the bike. The heat on the Electra Glide was an issue but as long as I was moving I didn't mind it, only in stop and go would I feel the burn. My 09 does seem to throw some heat but it has the mid frame deflectors so its not a serious problem
Edit- mileage on both the RK and the EG is around 40-45 miles per gallon. The EG would get about 50-51 on the highway doing 65-70 mph

 

My sportster is all stock with over 25,000 miles.
Your stock tune my not be as lean as most people believe.

I did buy a Power Vision and run Auto Tune many times.
My mileage has gone up 4 mpg on average this year. 48ish last year, 52 this year.
That is about an 8% improvement, so my engine was running about 8% RICH or about 13.5 to 1 with the stock tune.

The engine does run smoother with the VEs tuned by the PV.

Looking at the data logs from the PV, the closed loop (AKA lean) part of the tune is really only used to about 25-35% throttle. After that my stock tune is very rich at 12.5 to 1 AFR.

 

Most Harley's on the road have factory original AC's and calibrations. They run fine. The heat can be a problem especially sitting in traffic tie ups. But re-tuning isn't going to change it a whole lot unless you almost drown the thing with fuel. And that's not advised for a lot of reasons. The best way to cool it down is to install fans. They do work well. Harley's are pretty $$$. But there are some on the market just as good for less.

 

I'll tell you from years of racing experience, running lean over rich is what you want. Light grey spark plugs not oily or greasy.


Coming home from WY to Calif we ran across a 76 gas station that had 104 octane at the pump. We filled our tanks (we were all on empty). Bikes ran like a bat out of hell. The inside of our pipes were a light gray and our headers were glowing at the heads.
It was a crisp cold night and we had a blast running those tanks dry. Try some racing fuel and see how lean ya run.

 

The factory tune is just fine for your configuration. You have not changed the air flow (AFR) of the engine by changing only exhaust slip-on's.
As mentioned just be aware that it's not a good idea in your location to be stuck in 101°+ heat in a string of 12 stoplights or jammed freeway for an hour,,
,,but that would be for any air-cooled bike,, tuned or not.

 

Thanks for the input, all. It looks like I'm going to stay with the factory tune like I have been unless I do any mods that will actually affect air flow.

It was good to read others' accounts of staying factory tuned. I RTFF and researched some and the consensus was to stay factory tuned unless some mod actually affected air flow, which would be something beyond mere slips, but it was good to actually read an account with specifics and numbers from other riders across multiple bikes and lots of miles.

 

For less than $100 you can richen your bike up to about 13:8 to 1 with set of simple plug in XiEDs from Night Rider. Put them on my otherwise stock Street Glide, and they cooled the bike down nicely and improved throttle response a bit. Took less than 5 minutes to plug them in and zip tie them to the frame.

 

Just curious but how do you know your bike is "factory lean"? Whatever the hell that means


You obviously have no way of knowing what your AFR is without a tuner. And you should be doing better than 40mpg on a stock 103. As was said earlier you may not be as lean as you think

 

So I don't know what my actual AFR is, just that it's still factory tuned and I assume it's lean for emissions purposes. But maybe it's rich. I'll talk to a tech at the next service in case it's an issue, but for now I'll probably leave it unless I can get better mileage out of it. The performance is good enough for me.