Question about 2004 Yamaha WR 450 F

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I have a 2004 wr 450, when I got it out this year and started it I noticed that it pops through the exaust a lot. What can cause this?

Posted by Anonymous on


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  • Yamaha Master
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Hi, Anonymous popping or backfiring on deceleration is usually caused by a lean fuel condition or an air leak in the exhaust system and is generally located where black carbon soot is seen as a flashing build up from any joint connection. This condition can easily be remedied by removing and cleaning both joint pieces and reassembling with high temp silicone and torquing the exhaust clamp to the proper spec. Coughing is usually caused by an air leak in the intake system and will generally have the same telltale signs, a wet or damp buildup of oil/gas seepage at the intake manifold to cylinder head or carburetor to intake manifold connection and in rare instances a worn throttle plate shaft and or seals. Spitting is usually caused by a faulty accelerator pump and or nozzle, or the float bowl needle and seat leaking and overflowing through the main jet mixing well nozzle, or the air-fuel mixture screw is adjusted too lean. For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
2004 wr450 with bad backfiring issues Page 2 WR 400 426 450
Popping on deceleration
YAMAHA WR450F Owner Service Manual
OEM parts for Yamaha
YAMAHA WR450F Owner Manual

Posted on Oct 24, 2016


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Posted on Jan 02, 2017

  • 3567 Answers

SOURCE: rear coil spring change 2004 yamaha wr 450

I have never needed to replace that part so my best help is to put a service manual in your hands.
Go to this site and you can download a free PDF service manual. Most of the manuals are in English but some are not. There is no way to be sure without doing the download. You can always delete it if in a foreign language. The spring is the same '03 and '04.


Go to the site below where you can see a parts diagram for your specific bike. You will select the actual brand, year, model, etc., once you go to the site. Part numbers and prices are also shown. You can order parts from this site. In the event no price is shown on a particular part, the part is not in stock.

A “very helpful” rating for this answer? Thanks!

Posted on Jun 20, 2009

ollie reece
  • 1167 Answers

SOURCE: my 2004 wr 450 (120km only) has been sitting for 2

try for a spark take plug out and put against the cylinder and see if you can see a spark when you kick it over get back to me

Posted on Sep 26, 2009

  • 1508 Answers

SOURCE: what jet kit should i

JD jet kits give you a few options

I ended up using The red needle at 5 notches down
up from 165 to 170 main.
up from 45 pilot to 48 pilot

You might just want to try a 170main first and see how it goes

Posted on Sep 12, 2010

Mr BrokRench
  • 1623 Answers

SOURCE: Can't find oil cap on

The filler is on the side cover.

Posted on Jul 29, 2011

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1 Answer

2005 YAMAHA YZ450 The head is quite noisy. Have installed new valves and springs. New camchain. Oil pressure seems fine. I am thinking the auto decompression system on exaust cam is worn out / loose.

Hi, Colin for this situation I would call my local dealer or reputable shop's service/parts department and inquire about any possible quick fix, answers, or parts inquiry. For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
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Stripping my carberator on my wr 450f to clean, were could i get a pdf file mannual to help me plz!!

Please get it download in pdf and free at:
After you get online , choose file wr 450f, then download your manual Total file is almost 18 MB.
Regards, vote please, Jay

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I have a 2004 CRF 450 totally stock that had a top end rebuild about 6 months ago. I have had the bike out about 6X and i have noticed that when i let off the gas it backfires/pops more than normal. Also,...

Hi from Spain,

coul be related to lean mixture during deceleration that makes the exhaust hotter that make the blow-by gas to "explote". Check all carburator spec. are under standar, especially slow jet and slow screw adjustament.



Nov 29, 2010 | 2004 Honda CRF 450 R

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Im trying to start my 450 wolverine after sitting a yewar. It wont fire up,like getting no gas any ideas

having same problem, but i only left it for 5 months. Did you get it started? if so, how? or what was the problem? Thanks

Nov 13, 2010 | 2004 Yamaha WR 450 F

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Can you register a yzf 450 for street use

It would be possible but probably too expensive, there are some private compliance certifying companies that do the compliance plates for many of the low volume imports. but you would need most of the WR electrics and muffler. Easier to start with a WR and fit the YZ cams.
So even if you can find a WR wreck that has the compliance plate and rebuild it with the YZ bits,it would still need the WR;s engine number

Jul 24, 2010 | 2004 Yamaha YZ 450 F

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My 2004 wr 450 (120km only) has been sitting for 2 yrs and now will not start...where should I start for troubleshooting? Thanks Dave

try for a spark take plug out and put against the cylinder and see if you can see a spark when you kick it over get back to me

Sep 26, 2009 | 2004 Yamaha WR 450 F

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