A very good basic understanding of air fuel ratio's I think. And something to keep in mind when one wants to just throw on an intake or exhaust mod , and think that the stock system will be just fine... And remember for those here in the States at least, the vast majority of us run fuel with 10% Ethanol in it. So OUR Stoichiometric number drops from 14.7:1 down to 14.1:1 . So basically , to get to the same result, we need a slightly richer air fuel ratio .... MY 13.2:1 air fuel ratio for instance , maybe Europe's or Australia's 13.8:1 air fuel ratio or wherever Ethanol is NOT blended with the fuel .
https://www.youtube.com/watch?v=gPWI8QTRg9g These bikes come out of the factory with engines that are almost ? .... De-tuned relic's of the past . Tractor motors even ? Air cooled, Long stoke , over head valve, push rod and etc and etc.. Which gives them the charm and makes them fun to do performance stuff to. We are all really kids at heart and want to go faster ! Right ?! BUT.. they are set up for emissions ! And to pass Emission standards .. NOT for performance. From the dished piston , to the no duration no lift, wide LSA Cams. to the air box and the restrictive cat filled puny piped exhaust ! That's why people get on these bikes and wonder " THIS is a 500 ?!" And the stock EFI system is there to control this de-tuned motor ... IN... it's stock form . Once you go beyond stock ? You are playing with fire, depending on how you ride that bike and what you do it. Take the stock NARROW band 02 sensor that's in the head pipe for instance ... it's not there to tune your bike ?! It's there to.. almost fanatically!.. keep the motor running at very near 14.7:1 . For cleaner emissions ONLY . Well.... you can see that for performance and harder riding , and for when you go beyond stock You NEED a richer air fuel ratio .... Right ? Particularly here in the States. It IS an air cooled motor , and temp control is pretty good. But not AS good or consistent as a water cooled motor. So... why would you risk it with a TOO lean air fuel ratio ? Actually , your results may be too rich in some area's and too lean in others !
The latest batch of fuel controllers , No longer supply a o2 sensor cheater or optimizer. That is the devise that WAS used to cheat out the stock NARROW band sensor , so one could "tune around", it's wanting to bring you back to , TOO LEAN effects. And I believe these fuel controller company's are doing that, because they are getting too much HEAT from the EPA. Thanks VW and Harley !
Well ?.... That's fine for a WATER cooled motor ? But what about us ?! But no worries.... a o2 sensor cheaper is easily made with a couple of resister's and will still work the same as it did on a PC-V.
For now anyway...
An emission controlling NARROW band sensor needs to see about 700 degrees in that restricted head pipe , with that exhaust valve a few inches away. BEFORE it can start doing it's thing... and "correct the air fuel ratio" to around 14.7:1. And when would ones air cooled motor NEED the cooling effects of a more rich air fuel ratio ? Ummmmmm......
So... when that after market performance company is trying to sell you something .. that you just gotta have ! to go faster. Intake ,exhaust cams, heads . ANY change from stock ! Read that fine print, they ain't lying and it's nothing to scoff at and say " Ah... it will be fine. Joe blow around the corner has the same bike , and HE's been OK ? " But Joe Blow maybe pulling his bike out once a month on Sundays to ride to the Bar 20 miles away and sit there !