Has anyone installed a fcr 37mm on a 400ex?? Got a friend that has had a fcr 37mm given to him, and he is determined to install it on his 400. I’m up in the air about the whole mod in general at this point. Being that it’s downsizing as far as airflow(CFM) is concerned. I know it’s only 1mm smaller than stock so another part of me says he will gain the FCR’s throttle response in return. So where do we start with the main and pilot?? 400ex mods are: Big gun ES full exhaust, 11:1 stock bore, stage 2 HC, no lid/W K&N, AMR stage 3 CDI and stock valves and no port work. 175 – 180????? 40 – 45???????