why did it die!!!!!!!!!!

[02400exracer]

I have an 05 yfz with a HMF slip on, and the air box removed. I raced it in its first mx race and it kept dieing, it also has stock jets but it ran fine untile i took the lid off in the main. what do i need to do. thanks

[firefighterjosh]

It needs rejetted. It will run 10 times better if you rejet it.

[CHEVYZ]

My guess is that you engine needs to be retuned. 450s come very restricted stock and therefore come with extremely small jets. Now the bike has been opened up a great deal with the air box lid having been removed, along with the fact that your bike has a pipe. My guess is that your engine is starving for fuel and is therefore cutting off.

Put the lid back on. Then jet it for the pipe thats on it. Then once thats dune then take the lid off and mess around with the needle.

its much easier to jet doing it that way.