Factory throttle screw adjustment on 2003 yz250f

You more than likely need to adjust the valves check out dirtrider.com and search yz250f valve adjustment and that willwalk you through the steps hopefully this will solve you issue. It solved mine.

First, you shouldn't adjust the idle. If the idle isn't correct, that means there is an issue somewhere - not that the idle needs to be adjusted.

There isn't an adjustment screw. To adjust the idle, you will need to move the TPS (Throttle Position Sensor) forwards or backward. To do this, you will need to remove the tamper proof bolt and replace it with one that can be loosened and tightened.

There isn't an adjustment screw that you really manipulate. The computer dynamically controls the throttle using the information it gets from the throttle positioning sensor (TPS) on the throttle body. The TPS is secured with tamper proof bolts that the head breaks off when torqued down. If you remove the throttle body and extract those bolts, then you can add bolts/screws with head and can be loosened and tightened. Then you can move the TPS back and forth to adjust the idle.

I wouldn't recommend doing this though: if there is and issue with the idle, it is because something is malfunctioning, not because it needs to be adjusted.

you need to adjust the air screw on the carb it need turning 1 turn out not enough air getting through it

hope this helps

John

if you dont have a manual got to here and download one

http://www.mxguy.com/motorcycle-maintenance/2003-yamaha-yz250f-service-manual_01-16-2008/

LIGHTLY seat the throttle screw and air screw then turn both screws one and one half turns outward.This is the factory setting.

The air mixture needle valve is on the Carb. Throttle screw as you call it, you might be referring to 1- throttle adjustment at the twist throttle hand grip. 2- At the top of the carb is a throttle cable adjustment 3- some times somewhere between the twist grip and the carb there is an adjustment.4- there is also a idle adjustment at the carb.

try adjusting the clutch