I have a 450R carb freshly installed on my 400ex. I run with the lid off with outerwear and OEM filter. It has a 180 main so I'm thinking I'm running rich.

With the fuel screw out 2.5 to 3 turn Im good any less I backfire on deceleration. Problem I'm having is that it will idle ok but when I get ready to take off the slightest touch of throttle will kill it. I have to blip it a few times to get rpm's up then I'm ok. It's like its flooding it out. Do i need smaller pilot?

I'm not sure what my pilot is but assuming its stock. I can adjust the main jets but, i don't know how to tune for the needle position. Pointers anyone?

 

the pilot jet controls fuel from idle to 1/4 throttle. the neddle controls fuel from 1/4 to 3/4 throttle. the main jet controls fuel from 3/4 to wide open. run the engine for a few minutes at idle then check the plug. it should be light tan or gray. if its white then its lean and black its rich. change the pilot jet as needed. then ride the quad at half throttle and kill the motor with out idling down the motor. check the plug and adjust the neddle as needed. do the same for wide open throttle. its hard to make good jetting recommendations when no two bikes are the same.

 

Thanks for the reply. I know that each bike is different but was hoping someone who has done this mod would chime in and say "Oh stock pilot way to big for 400" or "Oh, have to move needle for 400".

I played with it more last night and found that anything less than 3 turns out on fuel screw will backfire on deceleration. Thought OK so it running lean on pilot. Got it at 3 turns and it quit backfiring but, it's rich. It wants to flood out on takeoff soon as I touch the throttle. Plus, I can smell it flooding.

 

move your shim up to the top notch on the neddle

 

well the carb is to big for the 400ex so if you do like a 440 big bore im sure it would work but im not sure if your gonna spend that money but if you want that to work you might have to see if the needle and jets of a 400ex fit in a 450r carb then [i dont know off hand] if some one else knows you have to mess around with the jets mixture and needle or maybe if you call up honda or the nearest dealer they might know

 

if they dont fit then you would have to mess with the 450r jets and needles

 

Have you gone to atvriders.com, ton of info on the 450r carb over there.