Where is the idle adjustment for your 1999 yz250?

The idle adjustment for a 1999 Yamaha YZ250 is typically located on the carburetor. You can find a small screw, often near the throttle linkage, which you can turn to increase or decrease the idle speed. Adjust it while the engine is running to achieve the desired idle RPM. Be sure to make small adjustments and allow the engine to stabilize after each change.