ok i have a 2005 kfx400 it start and idels good with the choke on and it will runs pretty good with the choke on but if i turn the choke off it spits and sputters pops and backfires even if you ride it 1 hour when you turn the choke off same crap. i pulled the carburetor off its clean i blem thu all jets all was clear no holes in my diaphram up top. its getting a good supply of gas when running any ideal im lost thanks mike

 

Your running lean for some reason. Why? Could be lots of reasons

#1 on the list is a plugged main jet.
#2 Plugged main jet passage.
#3 Air leak somewhere. (carb boot ect)

 

none of the above.

it's a plugged pilot jet.
when you pull the bowl off theres the main jet right in the center, then theres a little jet right next to it that is usually countersunk and you need a small narrow flat head screw driver to get it out.
take that jet out and make sure it is clean. and while it's out be sure you use some compressed air to blow out the orifice.
and also make sure your air,fuel mixture screw is set at 2 . turns out and that it also clean .

 

as stated above the carburetor is super clean i blew thru all jets the only thing i have found is the main jet cup is missing im goona install a new one of those and a dyno jet kit stage one i will post back what i find out

 

ok quick question how many threads are hanging out or how far in does the main jet screw in to the carburetor my main jet screw into the longer holder and the holder only screws in 2 turns i can email you a photo? mikesbikes@bpsnetworks.com

 

How does the engine start and idle good with a plugged pilot jet? The main jet comes on above idle and the engine idles off of the pilot jet.

To the OP. Your still lean for some reason. Why, your going to have to look harder.