Please Help Bring 03-WR450 back to life!

Hi all,

This will be my first post so please bear with me if I’m a bit noob-ish.

I am looking for Help / Advice bringing my 2003 WR450 back to its former glory.


So the story goes like this.

My WR450 was ridden both trail and road for approx 3yrs then due to a death in the family / the loss of the farm and my own kids being born the bike was put out of sight and mind. It has sat in a shed for the last 4 years to be exact!

Unfortunately it was not properly prepped before storage therefore was not drained of fuel, serviced or oiled. After much research I now realise the importance of this and my HUGE error in not doing so!


I have only recently been able to focus some money and attention on her with the intent to start riding again but can’t for the life of me get her started!

She did start and run reliably before storage, be it a little rough due to a broken mixture screw and also no working E-Start.


Here’s what I’ve done so far-

Full fluid and filter service with genuine OEM Fluids and Filters

Brake flush

New Starter motor

New Battery

New Spark Plug

Removed the Carb (it was dry but full of varnish from old fuel)

Cleaned out and treated the fuel bowl and jets with carb dip

Cleaned the needle valve as when I re-installed the carb it leaked fuel like a tap.

Installed adjustable mixture screw


Now that everything is re-installed and back together I just can’t get any life into the old girl!

I’ve tried         both electric and kick starting

Roll / Bump start

With and without throttle or choke

With “start you bastard” ether sprayed into the cylinder / intake

With fully charged jump starter connected

The closest that I got was one big backfire and flame pop from the exhaust on electric start?


I’ve checked and there is a spark, although it seems a little weak for my liking but I can’t find any loose earths or connections? Also should the coil boot grab the tip of the spark plug tightly? Mine seems to only loosely secure to the spark plug?

Would the spark plug be at fault seeing that it “has” backfired and popped a flame?


Sorry for the massive spill, I just figured the more info the better for you guys to help with.

I’ll keep trying and researching myself but any help or advice would be greatly appreciated J




I recently purchased a 2003 model that had been sitting for 3 years. It too, would not start. But I was able to get it to run for a few seconds using aerosol starting fluid sprayed into the carb throat. 


Just about all of its problems could be distilled into one word: Carburetor. 


I tried to clean the carb myself, but ended up taking the bike to the local dealer. He removed the carb, removed all the brass and plastic bits, and put it in a chemical bath overnight. It worked. 


Hope that helps.

Are you getting fuel to the carb? Have you pulled the petcock off, it may be gummed up and not allowing fuel to the carb. Looks like you've pretty much covered everything else.

Thanks guys,

I'm trying to do most if it myself, mainly as a project for the weekends, that's why I'm not fussed if it takes a while. Failing that ill be taking it to Yamaha or a bike shop :)

I tried to put what I could through a carb dip (mainly just the jets and bowl) but didn't want to get to carried away replacing seals an rubbers.

Yep fuel is defiantly getting to the carb (well the bowl at-least) I've drained it twice just to make sure. Also swapped tanks as the original tank had a leaky petcock, now have my safari tank on.

Here's the thing:


You did about 20% of what is needed to restore the carb.


Pulling the jets and making them shiny just isn't enough.


You HAVE TO DO IT ALL to make it work. It's a system.


...especially the passage above the pilot jet, which is probably still clogged, and you MUST use a new pilot jet, unless you cleaned hydrosonically. 

... especially the fuel screw and oring

...especially the apump diagragm and cavity.

....etc etc


If you clean the carb in Simple Green or Pinesol, it won't eat the body seal.

Edited by TheKoolAidMadeMeSick

Cheers! that's a heaps better tutorial than I was given by Yamaha, I initially saw them and asked if I needed to replace the jets. They just offered the carb dip and said that would be enough to clean them up. And to bring the bike in If it didn't work.

Looks like I'll be getting the carb out again!

Have a great time.

Write if you find work, or gold, or a clean carb.

Thanks bud, I'll get some new jets and give it a good once over this weekend and report back.

Fingers crossed !

Replace air filter, check fuel flow, check for faulty kill switch.


I'm stoked ! Finally got to have a ride !!! :)

Still lots on the To-Do list :|

I did a Massive tear down of the carb (thanks for the guide) full clean out of every Chanel, hole, jet and seal. Once back together she started up second kick and now I've run it a bit the E-Start is working :)

I think that it's running a bit Rich because it seems to "lurch" a bit when coasting at consistent speed /revs???

Still haven't had a chance to get new jets installed tho. Could that be the cause of the "lurch" problem? What jet would cause that?

Also I'm pretty sure I need a new needle valve or something because if the bike sits for a few hours the fuel bowl slowly drips empty (but even when petcock is turned off, so maybe not needle valve???)

Also on the list is

-Valve clearances

-Clutch adjustment (grabs just slightly when clutch is fully in, plus stalls when put into first gear When cold???)

-Figure out why the indicators only flash at high rpm???

-Somehow remove stubborn screws stuck in front brake master reservoir???

-New rear tyre and sprockets, plus adjust chain

-New indicator/light/horn button assembly to be wired in

-New mirrors (maybe just one anyway)

-Hard wire the trail tech onto the on/off switch

-Replace kickstand

-Paint some of the frame

-Scrub rims clean (any ideas on products or methods???)

If you are describing a 'studder' at very small throttle openings and constant rpm, this is a normal issue for the stock WR.

You can unplug your TPS from the Harness and fine tune your jetting to smooth it out.


-Clutch adjustment (grabs just slightly when clutch is fully in, plus stalls when put into first gear When cold???)  NORMAL
-Figure out why the indicators only flash at high rpm???  REPLACE YOUR RECTIFIER
-Somehow remove stubborn screws stuck in front brake master reservoir???  SLOT THEM WITH A DREMEL
-New rear tyre and sprockets, plus adjust chain  DONT CHANGE THE SPROCKETS UNLESS YOU CHANGE THE CHAIN
-New indicator/light/horn button assembly to be wired in
-New mirrors (maybe just one anyway)
-Hard wire the trail tech onto the on/off switch
-Replace kickstand 
-Scrub rims clean (any ideas on products or methods???)   USE NO ABRASIVES: JUST USE STIFF BRUSH AND DEGREASER

Thanks heaps for the info TheKoolAidMadeMeSick !!!

Yeah I guess a stutter is pretty accurate, although I can never remember it being that noticeable before.

Any ideas on the fuel dripping from the bowl? Like I said the petcock turns off fine so the fuel that slowly leaks is only what's left in the bowl???

Got quoted $200 for a new rectifier/regulator ???

Sounds a bit much to me ?

Your float valve is leaking, causing an overly filled float bowl

Remove and inspect for wear, if none, polish up the parts and cavity and test

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