High-G FJR Junkie!
Join Date: Mar 2015
Location: Rolling Prairie, Ind
The fact that you don’t need to rejet/remap when adding these systems should tell you all you need to know. It indicates that you’re not increasing the airflow through the engine so no need to add fuel. I would like to see a current fjr dyno sheet with a lambda sensor readout because when I got to spend time on my buddies Dynojet Dyno I was amazed at how rich most bikes ran once on the main circuits, these were mostly but not all carb’d bikes.
It showed me that the internet myth (and it is a myth) that all bikes are delivered from the factory extremely lean for emissions is nothing more than pure bs. Now I will add that most all ran around a 15-1 a/f ratio up to around 2000-2200rpm because that’s where they were required for emissions certification, above 2200rpm they all went pig rich around 10-1 to 10.5-1 a/f ratio, just pig rich which is why you can add a header w/o rejetting them along with the fact that all headers I seen tested made no difference past making more noise. The best you Could hope for was maybe a 2hp or so gain but most made less than the factory stuff, utter waste of money.
Now if you really want to gain some power you need to focus on the intake side as the fjr’s airbox is quite small for a motor of it’s size but be prepared to spend some serious money on dyno time tuning and reflashing things by somebody quite competent. If you just gotta have more power buy something else. My .02
Red 2014A, the fastest color !
Ride more,, worry less !
Last edited by passx; 07-19-2020 at 09:28 AM.