I bought a crashed 01 f4i this past fall and I have been building it into a stunt bike all winter. The bike was bone stock before me besides a M4 slip on. I had to replace the front end but once I got it riding again I noticed it had a bad bog/hesitation in low rpms. When you really get on the bike from idle or try to clutch up it falls on its face. It bogs whenever power is needed. It idles perfect and runs well above 6k rpm. I started with a throttle body sync then fuel pressure regulator. Then put a fuel pump in it and new plugs. I just recently replaced the entire throttle body assembly and all hoses associated with the fuel system. Still no luck. Bike has clean air mod and second idle screw. The interesting part is that there is no bog in neutral when the bike is revved up but if you shift into 1st and pull the clutch in and rev up the bike the bog is there. It's a very strange symptom and i have no idea what could be causing this.

Open to any suggestions

 

Does it have a Power commander installed??

 

Is it street fighter ? No ram air tubes ? If yes get some duct tape and cover the right side intake opening on the box. You are bogging down low because of excessive air intake. Once you cover this portion of the air box you should be good to go.

 

If you removed the fuel pump make sure you installed it back in the correct position and there are no pinches in the fuel pump lines. I made this mistake before and the bike started to bog at high RPM due do the the fuel pump line was not feeding enough fuel to the injectors.

Check your manual if you have one to see the correct way to mount it. I think the fuel line output should be pointing to the right side of the bike.