Frustrated

[Longtimeyamahaguy]

03 WR450, hard to start. Won`t idle unless I have the choke part way on. I have pulled the carb and cleaned it. Flames out the exhaust when it backfires. The bike did the same thing with the stock exhaust on it just not as bad. I just put a FMF pbomb header and powercore sa on it. Header turns cherry red when at idle for about1-2 minutes. I`m beginning to think I should have bought a YZ250 2smoker! I`m going to give this thing 1 more chance with some jetting if that doesn`t work out the first $3100 (without the FMF) will take this thing out of my garage!

[beezer]

Its obviously lean.

Stop whining and get a JD kit.

[Longtimeyamahaguy]

What is this JD kit?? I bought the bike used and it has a 168 main 48 pilot a few 70`s in it and some red knob hanging down in front of the bowl.

[jchantzWR400F]

What is this JD kit?? I bought the bike used and it has a 168 main 48 pilot a few 70`s in it and some red knob hanging down in front of the bowl.

OK, put the 4-stroke down nice and easy. Step back very slowly. Now turn and walk away immediately...

Seriously, get yourself a JD kit (through the TT store). It comes with instructions and recomendations based upon your riding condition (temperatures and altitude). Oh, and that red knob is the hot-start. If you pull it, it let's air into the carb-helps to start when you dump the bike.

[Dan_Lorenze]

It could be that you put on the carb slide-plate on upside down, I've done it, the bike will only run with the choke on when it's upside down.. Check it, and double check it with your manual...

OR-

Something is in the Pilot circut like a grain of sand, make sure that carb is as clean as it could be..

OR-

Check your valves, there's a small chance that the valves might be out of spec...

Change your spark plug....

Sorry, this doesn't sound like a jetting problem.... Even a poorly jetted bike should run with the choke off... A JD kit won't solve this one as you decribed it.. It's something more..

Dan

[Longtimeyamahaguy]

Slide plate maybe, plug is good, inside of the carb is/was spotless but there is always that chance of something falling in there. I`ll investigate tomorrow. Valves are just a tad loose on the intake but the exhaust seems good.

[Stinson]

3100 hmm, wouldnt mind having another 03.......

[flatnacker]

03 WR450, hard to start. Won`t idle unless I have the choke part way on. I have pulled the carb and cleaned it. Flames out the exhaust when it backfires. The bike did the same thing with the stock exhaust on it just not as bad. I just put a FMF pbomb header and powercore sa on it. Header turns cherry red when at idle for about1-2 minutes. I`m beginning to think I should have bought a YZ250 2smoker! I`m going to give this thing 1 more chance with some jetting if that doesn`t work out the first $3100 (without the FMF) will take this thing out of my garage!

How funny-I dont feel lone anymore, again exactly what my bike is doing!!

And I was thinkin the exact same thing-wish I had stuck with two strokes, so much easier to work on and trouble and maintenance free.....maybe I will change my tune once I have her sorted....

[hotrunnin-05wr450]

maybe I will change my tune once I have her sorted....

Yes you will!!

[RichieGoatGruff]

What is this JD kit?? I bought the bike used and it has a 168 main 48 pilot a few 70`s in it and some red knob hanging down in front of the bowl.

Then it's lean because the pilot jet is clogged....quit whining, take the carb off and blow compressed air thru all the jets, aftr you remove them!

[bg10459]

The red knob is probably the fuel screw, maybe a Zip-ty fuel screw. Does it have numbers 1 thru 4 on it? Check to see that it isn't turned all the way in as this will lean the pilot circuit. try backing it out between 1 and 2 full turns from all the way in. It works opposite from a 2 stroke fuel screw. in is lean, out is rich.