2003 WR450, red pipe, popping, and rough idle


8 replies to this topic
  • acarter92

Posted February 05, 2015 - 01:11 PM

#1

Hi Ya'll

 

I just picked up an 03' WR450, pretty much stock from what I can tell and doesn't seem to have a lot of hours on it judging by the condition. It has good power and does start right up. However it backfires (more like a popping, not a full blown backfire) on deceleration and has a pretty rough idle, not back enough that it will stall but not as smooth as it should be. Also, the first 2-3 inches of the exhaust are red hot after warming it up and revving it a few times on the stand. 

 

So, is this an obvious problem, like a carb adjustment? Just from doing some quick searched it seems like it may be lean... I can make and fix just about anything, but when it comes to carbs I usually stay away... I'll probably end up taking it to the shop, but if it may be something simple I can give it a try first. I know it'll be worth getting this bike running good. I used to have a WR400 and it was my favorite bike I've ever owned. Last summer I got back into riding and got a 2013 WR250R, it's a great bike after doing some mods, but I missed the power...

 

Thanks,

Austin 


Edited by acarter92, February 05, 2015 - 01:12 PM.


  • Krannie McKranface

Posted February 05, 2015 - 01:48 PM

#2

At the very least, read the FAQ's at the top of the forum

 

Very very very common problem

 

Carbs require maintnence, and gas requires treatment, or these problems will return

 

Do NOT take it to a dealer. They are not qualified, unless they sponser racers.

 

You can re-build the carb your self, upgrade it to current specs, and uncork the bike all for about $200



  • patrick2wd

Posted February 06, 2015 - 01:06 AM

#3

check if thers water in the fuel, condensation.. etc..

had that with my (othet) bike some time ago,

 

there should be a scew on the carb to empty it.. but make sure thers no water in the tank..

 

good luck!



  • flyandride

Posted February 06, 2015 - 06:40 AM

#4

Glowing headers are common with WRs.  If it idles for a couple minutes when it's warmed up, it will glow.  Usually not noticeable unless in a garage or at night.  It's been pointed out to me at a stop light by a cage driver.  

 

Carbs are not rocket science.  Look at the exploded views.  Clean em (Pine Sol in a crock pot) and read up on jetting.



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  • acarter92

Posted February 09, 2015 - 06:25 PM

#5

Thanks for the replies... After doing some reading I decided to mess with the fuel screw. It's very difficult to adjust the screw without removing the carb. I ended up taking a few things off to enable me to turn it enough to get at the screw with a modified screwdriver. I think I ended up turning the screw out about a 1/2 turn. It seems to be running much better, no backfiring or popping. My driveway is solid ice right now so once the weather improves I'll be able to take it for a ride to see. 

 

Thanks, 

Austin



  • flyandride

Posted February 09, 2015 - 06:43 PM

#6

Thanks for the replies... After doing some reading I decided to mess with the fuel screw. It's very difficult to adjust the screw without removing the carb. I ended up taking a few things off to enable me to turn it enough to get at the screw with a modified screwdriver. I think I ended up turning the screw out about a 1/2 turn. It seems to be running much better, no backfiring or popping. My driveway is solid ice right now so once the weather improves I'll be able to take it for a ride to see. 

 

Thanks, 

Austin

You can get a fuel screw with a knurled knob that sticks out the bottom which you can adjust with no tools.  You need one.  

https://www.rockymou...term=fuel screw



  • Krannie McKranface

Posted February 09, 2015 - 07:01 PM

#7

Please don't buy an aluminum fuel screw for a couple of reasons:

 

- they have a tapered tip, which is not the way the Keihin screw is (no taper)

- they are alloy, so they do corrode

- they do corrode, and eventually break off at the tip, if you accidentally bottom the screw



  • toten

Posted February 11, 2015 - 07:33 PM

#8

The JD fuel screw is brass with an aluminum knob, is it a good solution?

 

I agree that it sounds like a dirty carb. I'd suggest checking the valve clearances as well, if they get tight you can burn a valve and that's expensive. 



  • JVP

Posted February 12, 2015 - 04:00 PM

#9

I guessing you need to clean your carb.  I got five bucks in my pocket that says your pilot jet is clogged.  A hot pipe is normal on all four strokes.






 
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