Absolutely Buells run lean!
EPA emission standards (14.7 AFR) is lean for an air cooled motor! The only reason we run 14.7 AFR is to get a complete burn of the fuel to minimize emissions. If you want to get super technical going lean beyond 14.7 can cause an increase in NOx but from an emissions standpoint 14.7 AFR is the best compromise between HC and NOx output. Ignoring ignition advance, cats, egr, etc, other factors that play into emissions.
For an air cooled motor best performance is around 13.0-13.5 AFR. Of course the exact AFR for cruise, WOT, idle, etc vs. fuel economy, emissions, performance is debated to death. Some will argue in the 12's, some will run cruise low 14's or even stoich. But as you reach stoich there is a marked increase in temps, decrease in power, and greater risk of pinging/detonation. Water cooled. No problem at all. We can shed the heat and dump it via the radiator. Every car on the road! Air cooled. Got air? Eric added a fan to help but you are cooking sitting at idle. Run stoich at cruise when you have the airflow and temps are right, but at idle, wot, heavy throttle, etc run richer. Listen to every Harley rider complain and moan about it.
Remember back when we all tuned with carbs and reading plugs. I bet most of us were running in the 12's AFR, sucking gas, and leaving a nice carbon footprint behind. Our engines ran cooler and had more power! Then EPA increased regulations and the push for EFI, Cats, EVAPs on bikes. Ok I am ignoring the EPA noise standards too but I want to keep it simple. We didn't lean the mixtures on bikes out so we could run hot, header glowing, parade mode, prairie dogging, fan blowing furnaces. It was for emissions! Keep our grass greener, ozone layer, and grandma's asthma at bay! Of course everybody complained about the heat and the aftermarket stepped up allowing us to adjust our AFR's to get back to a more comfortable ride.
But the point is that Buells are designed to meet emissions standards. And those standards are lean for an air cooled motor. Our bikes were built for performance. Performance is not stoich! Fatten up the mixture and notice how your bike runs better, more power, doesn't cook you! I know I am generalizing here but I absolutely stand behind my statement that our bikes are lean. Ask every person on this forum what their reaction is when they tune their bikes and add fuel to their maps. Throw in free flowing exhaust and intake and you exacerbate the problem.
