I finished braking in my 400 that was just trail ported and at the end of a 300-400 foot run it feels like it is running out of fuel. The carb is still the stock one with a 310 jet. I was just wondering if this is a normal problem or do I need to start checking into my fuel system for a clogged filter or line.

 

You may need to increase your main jet. It is starving for fuel on the top end. Usually when you add a pipe or porting you must rejet.

 

Sounds like you have a piece of thash in your main jet. When the main-jet is cloged, idle to 1/4th is fine then it will start to bog when you get just over 1/4th throttle. Is that about what it's doing?

 

It runs great for about 300-400 feet then it falls flat on its face. It feels like the float bowl is running dry.

 

Yes because the main jet is to small.

 

what does a 400 come with stock?

Man that still sounds like somthing is cloged. Myn was running crappy... it did exactally as what you decsribed, I cleaned my carb and it ran like hell. Hey I have no clue about 400 jetting. Just my experience