Eratic Idle - Brand New 2005 WR450F

41 replies to this topic
  • BNutZ

Posted February 26, 2005 - 09:07 PM


Just picked up my WR450F today. The only "mod" performed so far was taking the silencer out of the exhaust. Once started, the bike idles ok then eraticly begins to idle. This happens without even touching the throttle. It appears that leaning the bike to the left cleared it up a bit and to the right made it pickup. (leaning it did not consistently resolve the issue everytime though). Blipping the throttle clears it up but it comes back after 15-30 seconds. A quick ride around the neighborhood and the idle still revs up on decceleration. Again, blipping the throttle seems to correct it. Thoughts, Ideas? It's obviously under warranty for the next 30 days but I'd prefer to not have to take it in and have someone tear my brand new bike down. Could it be a sticking float? I've checked the clamps where the carb meets the engine and they're both tight.

I'm discouraged but I know I'm going to love this bike once I resolve this eratic idling issue !

Thanks in advance.


  • gregwr450f

Posted February 26, 2005 - 09:26 PM


It sounds like a float problem to me, take it back to the dealer and let them worry about it

  • BNutZ

Posted February 26, 2005 - 10:16 PM


Although I'm not completely sold on the float at this point I'm guessing the best thing is to take it to the dealer. Unfortunately, I bought the bike in Mission Viejo (4+ hours from wher I live) so it's going to the local dealership here for the warranty work. I was just hoping it was something "stupid" that would either work itself out (gummed up / dirt in carb).

Just a follow on, i started the bike a few minutes ago and let it idle.. it rev'd up after 30-45 seconds... i left it..... it came down.... up.... down a little... back up... down..... then stayed up........ until I blipped the throttle.. :)

  • gregwr450f

Posted February 26, 2005 - 10:54 PM


Where is Indy when you need him :)


  • new2fourstrokes

Posted February 27, 2005 - 04:05 AM


mine done the same :p did all the free mods not sure what one fixed the problem but 1 of em sure did.. it is one hell of a fast bike now.. no problems at all :) :)

  • Dual_Dog

Posted February 27, 2005 - 07:17 AM


Just picked up my WR450F today. The only "mod" performed so far was taking the silencer out of the exhaust. Once started, the bike idles ok then eraticly begins to idle. I'm discouraged but I know I'm going to love this bike once I resolve this eratic idling issue !

Thanks in advance.


Did you try putting the silencer back in to see what happens? Did you try adjusting the idle up and down? I'd try these since they're easy and can narrow it down to either jetting or a problem with the float.

Good luck.

  • Dan_Lorenze

Posted February 27, 2005 - 07:31 AM


The pilot jet is responsible for idle. Make sure your bike is jetted correctly, these bike come real lean and it's possible that your dealer didn't set it up properly. I too have a new bike, I have a 170 main and a 48 pilot, the stock needle is fine. I don't really know of any float height issues with these bikes, it's possible but I would think it's something more common like jetting. Good luck.

  • BNutZ

Posted February 27, 2005 - 09:42 AM


Well, I put the silencer back in, warmed the bike up for a few minutes.. took it for a quick spin around the block and it kept dieing at idle. Adjusted the idle screw and got it to idle without dieing. Another quick spin around the block and the rev's stayed up on decceleration. :)

Argh.. I'm frustrated.. I just don't understand this.. I'm told that when the dealers put these bikes together they don't touch the carbs.. just uncrate the bike, put the front wheel on and fill it with fluids (oil/coolant/fuel). I guess I'll call the dealer and try and uncover some information as to how they set it up.

Without leading anyones thoughts, it seemed as if the eratic idle / rev's started to appear after the bike was completely warm (5 minutes or so).

  • berg

Posted February 27, 2005 - 10:19 AM


Hey BnutZ,
Don't feel alone, I also just got an '05 wr450 (Ca. model) and it is doing the exact same thing as yours. I took it out for the first time yesterday
to break it in. I have not done any mods at all yet. It seems to be more of the slide not fully closeing to me than jetting or an air leek causing it to lean out. I'm not too worried about it. I am planing on doing the free mods this week along with jetting and will have a close look at the carb I'll let you know what I find as soon as I get done.


  • BNutZ

Posted February 27, 2005 - 10:45 AM


Appreciate the response, not that I'm glad your bike is doing the same thing but it is somewhat comforting to hear that I'm not the only one. I spoke with the dealer down south this morning who stated he would have the service manager contact me tomorrow morning and work to identify the exact issue. The guys there seem honest and sincere and stated they would send (for free) any parts I needed.

Really looking forward to what you find for resolution on this issue.

Just for my own info, is it doing it without touching the throttle (i.e., start the bike, let it idle and it idles up... ) or does it only do it when you deccelerate? or both?


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  • alyupe

Posted February 27, 2005 - 11:25 AM


I too had the same problem. The first mod I made was blocking off the air injection and that corrected the problem. I have since re-jetted 172mj,48pj, lowedog ais block off kit (looks great easy to install) cut throttle stop, removed back fire screen in the air filter, and FMF muffler. All I can say is this bike is smooth and fast.

  • berg

Posted February 27, 2005 - 01:11 PM


To answer your question the idle hangs up on deceleration almost everytime unless the throtle is bliped, set idleing alone I've only noticed it
creap up once. Keep in mind I've only warmed the bike up a couple of times. I've allready got the lowedog ais kit so I'll make that my first mod tuesday nite and post the results here. I bet you'll have it all figured out before I even get mine up on the bike stand, so don't stress about it too much I've
got a feeling I'm really going to like this bike once I've got it all set up.

  • minion

Posted February 27, 2005 - 03:56 PM


mine done the same :p did all the free mods not sure what one fixed the problem but 1 of em sure did.. it is one hell of a fast bike now.. no problems at all :) :)

I would second that. I had the same problem with my new bike - it idled worth a crap. The first thing I did to the bike was re-jet with the JD Jet kit, and the problem went away.

  • BNutZ

Posted February 27, 2005 - 07:45 PM


In the past 8 hours I've talked to numerous people all who continue to state that the problem is Jetting / Smog Equip (AIS). I'm really looking forward to hearing how berg makes out with all the free mods / rejetting. I've got the service manager at the dealership in Mission Viejo calling me tomorrow AM so we'll see what he has to say. I really appreciate all of the responses received... if nothing else I'm SOMEWHAT comforted knowing I'm not the only one. Sure is a weird deal though...

Again, I appreciate everyones input, I've owned a thumper for a few years now but just joined this site... what an awesome community of 4-Stroke enthusiasts. :)


  • cgrlvr35

Posted February 27, 2005 - 08:07 PM


Bnutz the so cal man. I had the same problem. These gys on thumper know a lot. Mine was missing a fuel screw. Had to go to a second dealer after the first still couldn't get it right. Runs great now. Ive only done the baffle. Ill get into it. Great bike.

  • Indy_WR450

Posted February 28, 2005 - 09:08 AM


Where is Indy when you need him :)


I just got back from riding the WudI7 ride in HotSprings Arkansas!
Great single track! Fantastic weather and trail conditions! :p
You guys wont see much from me on weekends. I got to ride!

I agree with earlier posts:

48 pilot & adjustable zip-ty fuel screw.
AIS Lowedog kit.


  • BubZ

Posted February 28, 2005 - 10:57 AM


One other thing no one has mentioned that was common on Harley's is a small air leak in the carb boot. I have been fortunate, my bike idled fine stock and after I put the JD kit in still idled fine. But having spent some years on those ole HD's it might be worth spraying some carb cleaner around the rubber boots to see if the bike rev's.


  • jdd123

Posted February 28, 2005 - 12:17 PM


Everything I read, states that a hanging idle is because of lean jetting (pilot circuit). Removing your insert will make the bike more lean. You may need to step up to a richer pilot if you cannot correct this by turing out the fuel screw. Only go a maximum of 3 turns out. Check the 250F FAQ or thumperfaq in the 250 forum. There is lots of jetting info there.

I am assuming that your boot is not leaking on intake.

  • berg

Posted February 28, 2005 - 07:12 PM


No more eratic idle on my bike. I first did the ais removal mod from Lowedog, started the bike and it still idled like crap but did NOT HANG UP
as it did before. Next I went with the jd kit, removed snorkel,back fire screen and pea shooter mufler end. Thats all it took and the bike is good to go. Let me know how it works out for you, I will be out in your neck of the woods some time mid march so if you don't get it sorted out I'll see if I can help you out. You'll get it though, even if it idled correct you would still want the mods to make the bike all it is meant to be.

Good luck and keep me posted.


  • MortgageRider

Posted March 01, 2005 - 07:21 AM



What jetting did you go with? I'm doing Lowedog kit, JD kit, Zipty fuel screw, & YZ pipe this weekend. I'm having the same problem. I'm thinking 170mj, 48pj, & 70sj.



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