i think ole blue is running lean

2003 wr450 so far i have done the mods but now the carb needs work what shes doing is at 1/4 to 1/2 throttle the bike stumbles . half on up runs good but it does back fire when i let off . (note) the exhaust is un corked am i lean ? it has stock jetting . what is a good starting point ? with what size jets :)

i don't mean to come off as a jerk but this is your second post asking for jetting specs. there have been replys. 48 pilot, pilot fuel screw (it is not an air screw like old two stroke carbs)at least one and a half turns out, jd needle kit. some people use the yz 450 needle but i have found that the jd needles give much smoother power. i am using the blue needle right now, clip in the middle. moving the needle clip one position can have a big effect on the low rpm bog. if you check out the jetting that is given at the bottom of members posts you will learn a lot. good luck.

Buy the following:

JD jetting kit from this TT store, 48 & 42 pilot jets, 72 & 65 starter jets, zip- ty fuel screw from Zip-Ty Racing products.

Jetting advice after you have the right stuff is very easy.

Just let us know your altitude & temperature and air box mods/ pipe (corked or uncorked) for the best set of recommendations. :)

Alrighty then,I have an 03 wr 450 and this is what she's doing. The bike ran great up to this point. I am running a 155 mj,48 pilot,air fuel screw @ 2 turns out,everything else is stock. I just did the Rob Barnum (Barnumspro.com) air box mod.Whick looks trick by the way! Anyway the bike is running to lean now, it's popping,shooting little flames out the exhaust. I turn the air fuel screw out as much as four turns but it doesn't cure it? I was told to first go up in the pilot jet first, then raise the neeedle one position next if that didn't help it. What does anybody else think? Before I do any changes, I stuffed a towel in my airbox to see if that helped, and it did.So I know that the bike is running to lean. Thanks!

"Oak Harbour" Washington. Sounds like you are at sea level (I would put your alt. and temp. bike and current settings in your sig. This will be a sure way of getting a response from the jetting guy's.). I'm not a expert at jetting, but at sea level you should be running around a 170 mj in cooler temps.

Yeah lift that needle for sure,you will probably need to go up on the main too,but lift the needle first,also mark your throttle positions on the throttle housing at the twist grip to help you out,mark a line on the grip and housing for closed,twist the grip open for full throttle then mark the housing next to the mark on the grip,then do the same for 1/2,1/4,3/4,will help you in the same way blocking up the air box did to confirm your problem! :)

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