Sorry to ask this again but I seem to have a mental block with this issue. I used to know the answer but I am now having indecision. It's a bitch getting old!
Do our bikes run leaner in cold weather or warm?
Please, no flaming, I promise to write it down this time! LOL!
Thanks

 

The bikes run leaner without adjustment in the colder temps. Think of it as when the air gets colder, then it is smaller and more can be packed in there with the standard amount of fuel.

Also if you will note, when it is colder (below freezing) the air is generally drier.

I had to learn this from many years of racing motocross and living in the north central region.

 

Thanks. That's what I was thinking but glad you reinforced it. My bike runs better in warm weather.

 

If ur bike is injected it doesn't matter

 

It actually still matters......just not as much. Granted the electronically controller (injected) bikes can make adjustments, but not as broad as you would think. Where you might have to rejet a carb every 20 degrees to make it work effectively, you can get away with 50 degree differences with the injected bikes. The narrow band O2 sensors are not able to make up for the great swings in temp.

In Wisconsin, I have personally rode my injected bikes at temps as low as 20 F, and as high as 105 F. You can tell that it runs better at one end or the other. My race bikes were tuned to the point where I would have to change the jetting during the racing day as I only had a window of about 15 degrees on the carb. Start the day with practice at 70 F and race the last moto of the day when it was 98F.

 

I actually lean mine out in winter...I'll explain. Remember the reference AFR is 14.7.

I have the Vied's, so i can run from 14.3 down to 13.8. In summer I'll run 13.9 to 14.0 which is considered "rich" (er). So in winter I run it at 14.1 or 14.2 which is leaner than summer.
In summer, it's best to rucn a bit rich to keep the exhaust cooler. In winter...the heat isn't as much an issue.

 

dohadex,

You are also in Florida where there is more humidity. Also as you stated in your comment, you are working to manage heat and heat isn't as much of an issue in the winter time. Remember that fuel and oil are two of the three key cooling agents in these motors.

When racing we wanted our motors as lean as possible to insure crisp throttle response, maximum power, and economy. The reason that we wanted economy was so that we could run less gas for less weight. But when you run lean, your motor runs very hot, so it was a constant dance to keep your motor from melting down.

With you being able to have a lower air temperature, that means that you can stand a little more engine temperature. This will give you a crisp throttle, maximum power, and economy.

 

Not so.
My AFR changes significantly from summer to winter. My bike is an 06 NON-O2 controlled Delphi EFI, this system is often overlooked or completely disregarded. Oh well, still more precise fuel delivery than a carburetor. I basically settled for two maps, one above 70F, and one below 70F, not unreasonably inconvenient.

 

Hot lean, cold rich basic physics. Fuel injection helps.