I just bought an 05 YFZ450. It will not idle during warm up (both full choke and half choke) without me giving it a little gas. Can any someone recommend what carborator adjustment needs to be made. Thanks.

 

Just bump up your idle a little. Your owners manual should illustrate it's location if you're not sure.

 

It’s not a good idea to let you bike idle and warm up. During idling, the oil is cold and think and the oil pressure is very low. It takes time for the oil to move around the motor and lubricate things correctly. Long idling also causes the piston to stay cold for longer. During this cold combustion, acid forms inside the combustions chamber and over time will cause the metal to be corroded. When the motor is warmed up, there is no acid being formed inside the motor.

I have seen Raptors and YFZ450's with messed up heads and cams. The cams do not get the correct lubrication and it grinds the metal on the head and cam. Very soon, you have to replace both and its not cheap.

The best way to prevent this, is to start the bike and ride it. Do not exceed 1/2 throttle until the motor is warmed up. This does two things. The motor warms up much much faster. The oil pressure is much higher at riding speeds and oil circulates much quicker. The time for acid forming in the motor is also kept to a minimum and the motor will last longer.

Do not rev the motor to the max until it is warmed up!