Where Next For 04 Wr450 Running Rough?

My 04 WR450 was running fine and has been for more then the two years that I have had it. Then all of a sudden it just started running rough. I mean beginning of the day it was fine (and this was even at a track) I came in early on my last time out because it wasn't running correctly. The bike was jetted before me and has an FMF pipe on it.

Everyone said the carb was probably just dirty, so I pulled it and cleaned it. Looked good except the pilot jet screw had some gunk around the base of it (looked like a destroyed o-ring) Cleaned that and the holes at the end of it and also pulled all the othere things and made sure they were clean and open (they all were). When I first saw the dirty pilot jet screw, I was thinking great... that has to be the problem.

Put the bike back together, fired it right up made a few adjustments to the fuel screw and it seemed to run better. I put on some new radiators and took it for ride and it seemed to be right back where I started. It would fire up nice, I could twist the throttle hard and it would sound good.

I took it for ride about a week later and it ran rough (still firing right up and the throttle twisting hard was good) Took it out and lots of hesitation. Pulled it back into the garage and completely removed the carb this time (throttle cables, etc...) took it all apart, top section etc. just to see if anything looked dirty. It looked fine, but this time I also purchased a fuel mixture screw so I put everything back together and fired it up. Started right up, sounds good, twist the throttle good, I drive down the road a little and it feels good (like how it was before all this) Granted I am only in first and second. (when I say good also, I mean the thing has always had little backfiring on decel, but zero hesitation when twisting the throttle) I wait a little later for it to get dark and take it out on the back roads so I could get up into the gears more.

Bike seemed to be good. Riding good through the neighborhood, first and second. Pull out onto the road and take off, first, second, third... and then the hesitation..... I let off the gas and it just stalled, I dropped the clutch if fired back up but then ride back off as I coasted to the side of the road. (now I am sitting there on the side of the road with all the cars passing me, hoping one of them isn't a cop wondering why I am riding it on the road). I tried to start it, but got nothing. After about 2 minutes of trying that, I just started pushing it back and trying to start it as I walked and after about a minute of walking, It fired up, I jumped on and road it back towards my house. It seemed okay again after it started, but then it started to hesitate again and then stalled again.

This is my first time ever doing stuff on a bike, so I am looking at it as a time to learn about the bike even though it is being sold. I really just want to get it back to how it was and just trying to figure out what my next step is. I am not really sure what it all means, but am hoping one of you has my next step to try based on the explanation I have provided.

Any help is greatly appreciated. I can pay someone to fix it, but am hoping to get it done on my own (with the help of this forum)

Thanks, the new bike has EFI, but still just trying to learn on this one.

Edited by 74dirtdown

From the information you've given me, I'm leaning towards the ignition coil getting hot and shorting out, which would cause the intermittent problem you seem to be having. Although the dirty carb has me concerned too. Do you have a manual? Maniac

Yes, I do have a manual.

What do you think about working the fuel mixture screw out more? I mean I am going to try that tonight, but just trying to see if that would make any difference with it seeming to run okay in the beginning with 1st and 2nd, but then when I took off, it seemed to maybe not have enough gas with the hesitation.

I also have a 04 wr 450. I bought it used in 07 from a guy who took good care of it. After three years and many miles, I had rouigh running, hesitation, bog, etc. My friend and I tried everything to resolve these issues, doing the work ourselves over the next two tears. Nothing worked. I had almost resigned myself to settle for a crappy running bike. Time to spend some money and let the pros handle it. The shop I took it to (Pit Pro in Newhall, CA) identified one of the prolems as hot start valve body (?) had a crack in it and was sucking dirt. They replaced it. Next problem was the dirty carb, and slide wear plate needed to be replaced from excess wear from dirt. They sent the carb out to a carb shop, and they ultrasonic cleaned it and rebuilt it. When I got it back, it ran better than it has ever run. Starts right up, runs smooth, no bog or hesitation. Some times you just have to let a pro handle it (and stop being cheap!). Along with the suspension upgrades and tuning (also done at Pit Pro) , it is a joy to ride my bike again.

From the information you've given me, I'm leaning towards the ignition coil getting hot and shorting out, which would cause the intermittent problem you seem to be having. Although the dirty carb has me concerned too. Do you have a manual? Maniac

Check the coil. it will act like the carb is messing up.

I think I have an extra coil you can try if you need.

Also follow the hot start cable into the top of the carb. See that little black plastic piece? Is it broken?

Look at the wire that comes out of your starter button up on the bars. Make sure it is clear from your break perch. Mine rubbed against my perch, bike ran weird until it didn't run at all.I DNFd the race and I was very disappointed. I thought for sure I toasted the top end but it was something that I shouldn't have let happen.

email me at international4strokerecyclers@Gmail.com and if I have a coil ill mail it for you to isolate your problem. I have never had an issue with the coil on my WR but I have heard if people that have

And one more thing

pull the vent line off your gas cap

I have heard of the one way gas flow thingie malfunctioning and not allowing gas tank to vent. If that's the situation a person could throw hundreds of dollars at the bike before they figure it was a two dollar part

Let us know what does or doesn't work.

Maxpower is right! I've had the one way valve on my gas tank cause all kinds of problems, and it took forever to diagnose it!!! Personally, I would pull the fuel tank and completely clean it, including the fuel petcock screen. Then while the tank is off, I would check every wiring connection by removing each one and then reconnecting it, making sure it seats fully. Then clean the carb again. I know, I know, it's a lot of work, but either your carb is getting dirty or you have an electrical issue. After you've got the carb cleaned again, I would install one of those clear fuel strainers in the fuel hose right before the carb. This way you can see if any crap is making it into the carb. If you've cleaned your fuel tank properly, you don't need the clear strainer though, so it's your call. Let us know if any of this helps! Maniac

Thanks. I am going to give everything suggest a try and see what I get. I think I am also goign to have MaxPower send me that extra ignition coil just to rule that out. I'll update this post after I get done with the other stuff.

I had a similar problem on my 04, unfortunately when it went south it was 30 miles from camp back in the forest. It took us two days to tow, tug, push and drag it out of some very unforgiving terrain...and when it was all said and done, it was the coil.

Edited by dez4ever

Just wanted to give an update. I went through everything and not exactly sure what part did the trick, but the bike now runs better then it ever did. No more backfire on decel, starts easier with not backfire (never had a problem starting, just starts that much quicker, faster, better now). The final test was yesterday and I road for about 30 minutes without any issues and the bike felt great.

Thanks for the ideas and help.

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