2003 WR450 HELP ME!!

I am aproud owner of a brand new 2003 WR450 and have uncorked the exhaust, installed the YZ throttle stop and pulled the airbox baffle. Now my bike bogs down bad when I twist my throttle, anyone have an idea where I should turn? I replaced the throttle stop but still have the bog, could my spark plug be giving me the trouble, pulled it and it is really black and sooty.


Your off to a good start, now go to "Jetting Q's" on this forum and start reading. I ride in west central IN and I changed to a 160 main jet and a 48 pilot jet. I'm pretty darn happy with my 450.

You've come to the right place to learn about your bike. There is truely a wealth of information available here.


i did the same exact mods and just changed the main jet to 152 and was good

i also turned the fuel accelerator pump clockwise to get rid of the bog i am running at about 3000 feet

If I were you I would take my carb off and make sure that the jetting is stock, who knows what the dealership did. Just start from scratch. My bike runs perfect with stock jetting, yours should too.


I agree with Dan. My bike has stock jetting and it starts good and runs great all thru the throttle. I haven't done a mod except pull the silencer out, not sure yet about GYT or PMB. To install a YZ number plate do I need to make some brackets because of the odometer?

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