Lean is mean? Harley EFI & Harley Carb Discuss Lean is mean? in the Harley Tech & Harley How-to forums; Everybody I talk to tells me LEAN is mean!!! How true is this and can you run them to lean?...

[jc94]

Everybody I talk to tells me LEAN is mean!!! How true is this and can you run them to lean?

I don't know about being mean, but too lean will cause the engine to run hot and can damage it over time. The idea for a perfect tune is not too rich, not too lean. Achieving that goal is the hard part. Being near perfect from idle through various throttle positions is very hard to do for perfect combustion mixture. That is the art of tunning whether it be carb or EFI. and the goal. Because of limitations with carbs most end up on the rich side overall. With EFI there are more enhanced options through out the rpm range to play with. But a perfect tune is very hard to achieve. Running very rich can foul plugs, drop gas mileage, and build carbon.Too lean can heat up and destro y engines. Most of us settle for somewhere in between. Dyno runs can help get tuned as close as you're gonna get tuned for power.

[shovelmike]

The only way in which I feel "lean is mean" is in terms of a bobber running only running the bare essentials- no fat.

[rjrivero]

Great Subject.

Alot of folks try to change their air filters, and go to aftermarket pipes on their EFI pipes. These filters and pipes flow very well, and can in fact cause a bike to run lean. It will hesitate, and generally run like poorly. Throttle response will be sluggish, and it will hesitate.

You have to match the fuel delivery to the air delivery in order to obtain a good Air to fuel ratio or AFR.

The debate becomes, what is the optimal AFR?

Stoicheometric AFR is 14.6 to 1. Meaning, you need 14.6 parts of air to 1 part of fuel in order for there to be enough oxygen to burn every bit of fuel in that mixture.

So, you should never run more lean than that. The closed loop EFI's will try to acheive stoicheometric afr in part throttle cruizing, and idle conditions. It is most efficient, and clean. However, you will find it is also HOT. There have been alot of folks complaining about the high temperature of the new closed loop efi bikes.

Folks claim that you can get Max power with an AFR of 13.2. So the race tuners reccommend you use 13.2 for your baseline for when you're tuning your bike per the manual for the race tuners.

At higher RPM's at WOT I like them to be as low as 13.0 as my bike feels like it's pulling more around that setting.

I lean it out to 14.3 at highway cruising at part throttle. (Leaves a bit of margin for error depending on etoh content and altitude as well as different gas grades in other parts of the country.

How do you know if your bike is lean or fat?

You need a o2 sensor, like on a dyno with an exhaust sniffer.

I use a twinscan II plus from daytona twintec to monitor my exhaust gasses.

RJ

unless you're looking for et's, lean is just an unnecessary gamble. A bit on the fat side is not only safer, cooler but with most engines, especially v-twins, a bit rich is perceived as "torqie" and mapped this way purposely for that reason - for the "STREET".