I have a '99 F4 and next to my fuel filter there is a twist **** with a phillips square head in the middle, that i can turn to the left or the right, and when i turn it to the right it makes my bike idle lower or if i turn it to the left the bike idles up... wtf is this!?!? ive noticed when its turned more to the right it seems smoother when i rev it out but maybe its just me, haha i dk. but i havent the slightest idea what it is, anyone know??

 

Its the *Throttle Stop Screw*.

Factory Honda Service Manual Section diagram 1-23 & section 3-14 p58 photo & operation (online links avail here on forum).

Your RPMS should be btwn 1300-1500 RPMs. I keep mine at 1400 RPM.

 

yep.. gotcbr got it!