Air box question

I have recently got a 2000 wr400. The first mod I made was to remove the airbox lid. In doing so the header started to glow really bright. I then put the lid back on and the header didnt glow as much. Do i need to re-jet with the lid off? Also I get the occasional backfire on decelleration, the air screw is 1-3/4.

Thanks for any advice.

More air in means leaner jetting. Try backing out the air screw another half turn and if this helps you'll probably have to go one bigger on the pilot jet. As for the glowing headpipe, they all do it if they are allowed to sit and idle.


Hey Ernie, you're a former two-stroke guy right? The WR/YZ (and all four stroke motors) don't have air screws, but they do have fuel screws. Just clarifying :)


You are bad. I was working on my YZ125 earlier that day and I had a brain fart for a second there.


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