2003 WR450 Carb Problems

Alright, so I was bad I know. I bought a new YZ so my WR has been getting pretty neglected over the past few months. I took her out the other day and it just didn't want to run well at all. She starts on choke just fine, but you pull it off choke and it wants to die. Get going on it and let the main jet take over and she pulls like a son of a gun. Something in the slow circuit, right?

So I pull it apart, all the jets come out, starter, pilot, main, pilot air, and AP leakdown, oh and the A/F screw as well. I pull the AP apart give it a cleaning, pull the Air cut apart and clean it as well. I shot carb cleaner in every hole, nook, and cranny I could find on this thing, then blew it out. I put it all back together, put some fresh gas in it, and she fires right up. It sounds really, really good when I push the choke in initially, but after about 10 seconds it starts running like poo again. So any thoughts?

And just an FYI, all the free mods have been done, and the TPS has been unplugged for about three years with no big problems.

Alright, so I was bad I know. I bought a new YZ so my WR has been getting pretty neglected over the past few months. I took her out the other day and it just didn't want to run well at all. She starts on choke just fine, but you pull it off choke and it wants to die. Get going on it and let the main jet take over and she pulls like a son of a gun. Something in the slow circuit, right?

So I pull it apart, all the jets come out, starter, pilot, main, pilot air, and AP leakdown, oh and the A/F screw as well. I pull the AP apart give it a cleaning, pull the Air cut apart and clean it as well. I shot carb cleaner in every hole, nook, and cranny I could find on this thing, then blew it out. I put it all back together, put some fresh gas in it, and she fires right up. It sounds really, really good when I push the choke in initially, but after about 10 seconds it starts running like poo again. So any thoughts?

And just an FYI, all the free mods have been done, and the TPS has been unplugged for about three years with no big problems.

Carb cleaner is a no no, unless it is MC carb cleaner. Auto cleaner will ruin rubber parts inside.

Your pilot jet is still clogged, and probably so is the passage above it. Replace the pilot.

I agree the pilot cicuit is probably clogged again , I just cleaned the carb on my friends 98' 400 and had to disassemble it three times due to a similar running problem.

I ended up running a piece of .020 safety wire down through the orifice just aft of the airscrew inside the body which is the pilot jet exit and dislodged some crap that wouldn't come out blowing it the other way with air.

If you have crap in that large passage, you will probably have a clogged apump nozzle too....

I agree the pilot cicuit is probably clogged again , I just cleaned the carb on my friends 98' 400 and had to disassemble it three times due to a similar running problem.

I ended up running a piece of .020 safety wire down through the orifice just aft of the airscrew inside the body which is the pilot jet exit and dislodged some crap that wouldn't come out blowing it the other way with air.

So one question, is that orifice straight through or does it have any bends in it? I've tried wire through it, and it's a no go but before I try harder I want to make sure Yamaha in all their wisdom didn't put a bend in the passage for some strange reason.

Yes there is a bend in it. i used the wire to dislodge the obstruction at that end of the circuit then blew air down into it to blow it out where the jet was removed from..

All better now! Thanks for the help guys. It did take a little working around to get a small piece of wire through the pilot orifice in the throat of the carb but it finally went and out came a bit of crap. I put it back together, and she runs like a champ. Heck even the AP runs better now which makes me think it had some sort of clog that is now cleaned out.

Now the bad news is that it is time for me to sell it now that I've got it running well. With the YZ in the garage I just don't ever ride my WR anymore.

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