yz400f advice needed

99 Yz400F


Finally got the bike running with a carb rebuild. Now i can start on fine tuning it.


Bike starts like a PITA. Choke on, Hot start on. Soon as it fires, take hot start off. Upon riding, power is ALMOST all there. Lots of popping. Idle screw does nothing, bike wants to die unless you keep giving it gas.


Carb is all rebuilt, with factory jets.


Where or what should I start with? I have many jets here.




Valve clearance was checked. There all in spec. Intake is a tad tight, right at .020.


Exhaust has a slight leak at head / header mating part, I will fix that as soon as bike cools down.


Would like to atleast get it to start a little easier, and figure out why idle screw does nothing.

Edited by chrisx88

Hey there mine was doing almost the same thing on the fuel mixture screw there's a small o ring make sure it's not ripped or deformed

Or just missing.

Oring is there.

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