Change idle jet, 2005 WR450

[rpaitich]

Some help guys...

I just got a nice 2005 WR450 for my son to ride with me.  It only runs well with the choke out.  A buddy told me it's probably a clogged idle jet.  It looks like a challenge to get to the jet, but he told me that some models of WR450 allow you to loosen clamps and rotate the carb, and get to it thru the drain plug.  Any advice appreciated.  Yeah, I could give it a shot on my own, but it would be better hearing form someone who's done it.

 

Ron

[flyandride]

That sounds like the typical clogged pilot jet.  On the steel framed WRs you can loosen the carb and rotate it enough to take off the bowl and pull the jets.  You may have to remove the hot start plunger if it comes off the top.  I've done it on my 250, I have a later 450 also, on those the carb is buried.  

[FORMA MOTO]

 Yes, loosen boots, rotate carb to the kickstarter side, not the shifter side.

The hot start nut on the top of the carb is hard plastic and breaks easily to be careful

You will probably still have to lay the bike on it's side, wear a headlight, and have a plethora of different Phillips head screw drives, knuckles, or flex ends.

 

The screws on the float bowl will strip in an instant if you use a standard Phillips bits, because they are not Phillips, they are ISO heads.

You can make an ISO tip by grinding 1mm of the end of a #2 Phillips screwdriver/bit.

 

...and they may still strip, so squirting them from the top (the exposed thread holes) with PB Blaster is a good idea.

[mrgem]

The rubber "joint" (or boot) that creates the passage between the carb throat and the intake on the motor has little "cutouts" that are keyed to small bumps on the carb and intake. Make sure you don't tear the boot at these points when rotating the carb.

[beezer]

You can access the pilot jet from underneath through the drain plug on the float bowl.

 

I lay a small mirror on the cases underneath the float bowl and use a shorty screwdriver.

 

Takes 1 beer and 2 F-bombs and it's done.

[06gixxer1k]

 Yes, loosen boots, rotate carb to the kickstarter side, not the shifter side.

The hot start nut on the top of the carb is hard plastic and breaks easily to be careful

You will probably still have to lay the bike on it's side, wear a headlight, and have a plethora of different Phillips head screw drives, knuckles, or flex ends.

 

The screws on the float bowl will strip in an instant if you use a standard Phillips bits, because they are not Phillips, they are ISO heads.

You can make an ISO tip by grinding 1mm of the end of a #2 Phillips screwdriver/bit.

 

...and they may still strip, so squirting them from the top (the exposed thread holes) with PB Blaster is a good idea.

 

And that is why I now have one of these   I forgot to disconnect the hot start before tilting the carb.

 

[rpaitich]

Thanks to all of you who responded.  I now know how to approach this; with a couple beers, I'm set to go.

Ron

 

PS...what's that red gizmo in the pic?  ...an aluminum replacement for the plastic hot start nut?

[06gixxer1k]

Thanks to all of you who responded.  I now know how to approach this; with a couple beers, I'm set to go.

Ron

 

PS...what's that red gizmo in the pic?  ...an aluminum replacement for the plastic hot start nut?

 

Yes. I broke the plastic piece when tilting the carb to access the jets and replaced the broken OEM plastic fitting with this one.

 

http://www.amazon.com/Pro-Circuit-Start-Fitting-HSC04250/dp/B000GU16H0/ref=au_as_r?ie=UTF8&Make=Yamaha|1210&Model=YZ250F|20761&Year=2003|2003&carId=001&n=15684181&newCar=1&s=automotive&vehicleType=motorcycle

[rpaitich]

Yes. I broke the plastic piece when tilting the carb to access the jets and replaced the broken OEM plastic fitting with this one.

 

http://www.amazon.com/Pro-Circuit-Start-Fitting-HSC04250/dp/B000GU16H0/ref=au_as_r?ie=UTF8&Make=Yamaha|1210&Model=YZ250F|20761&Year=2003|2003&carId=001&n=15684181&newCar=1&s=automotive&vehicleType=motorcycle

 

OK, got it.  I suppose it would have been obvious if I'd looked at the carb.  Duh.

Pricey little devil, but eliminates the problem.  Thanks.

[rpaitich]

Thanks for the advice above; I got to the pilot and "starter" jets.  Not too bad.  Nothing broken.  Yet.

 

But when I removed the pilot and starter jets, I found both were clear, no clogs.  This is a new bike to me; despite 40 years of OHV riding, this carb has lots more to it than I've seen.  I found a red knurled knob on a 2-inch shaft, through the bottom of the float bowl; it has the look of a mixture adjustment.  My big factory maintenance manual doesn't show this.  Could this be why the mixture was too lean, requiring the choke to run at all?  Hell; I looked in the normal places for a mixture adjustment, but didn't think to look UNDER the carb.  I didn't see it earlier, but I hope it's accessible when the bike is back together.

 

I see in the manual that there's a pilot air jet and a leak jet.  Are these suspects in my too-lean running?

 

Thanks

 

Ron

 

 

---------------------------------------------------------------------

Here's what I found made it easier to get to the jets (for those who haven't done this):

* remove plastic and gas tank

* disconnect throttle cables at hand group, to allow length to rotate carb

* unscrew red hot start knob (to avoid breaking, per 06gixx above)

* rotate the top of the carb toward the kickstarter until the float bowl is clear

* unscrew four phillips screws in float bowl 

[FORMA MOTO]

The knob is the fuel screw.

It only affects idle to 1/16 throttle\

Leak jet only affect quick throttle openings (apump squirt)

Pilot jet should be 45

air jet should not be changed

 

Are you looking inside the pilot jet, with the (8) micro sized holes on sides?

[rpaitich]

The knob is the fuel screw.

It only affects idle to 1/16 throttle\

Leak jet only affect quick throttle openings (apump squirt)

Pilot jet should be 45

air jet should not be changed

 

Are you looking inside the pilot jet, with the (8) micro sized holes on sides?

 

I speculate that taking it out, CCW, will make the mixture more rich.

So if this adj covers idle to above; this seems like a candidate for the choke/idle problem I have.

Hmmm; I'll look at the pilot more carefully for those tinny holes; I was looking straight thru.

[FORMA MOTO]

I speculate that taking it out, CCW, will make the mixture more rich.

So if this adj covers idle to above; this seems like a candidate for the choke/idle problem I have.

Hmmm; I'll look at the pilot more carefully for those tinny holes; I was looking straight thru.

 

No, must start with the pilot first, then the fuel screw.

Just put in a brand new 45 pilot and be done with it.

Clear the passage above it first with fishing line and compressed air.

 

Don't over think this.

 

You don't guess turns for the fuel screw, you turn it for max idle.

 

Read the 'how to set your pilot' in the jetting forum.

[rpaitich]

No, must start with the pilot first, then the fuel screw.

Just put in a brand new 45 pilot and be done with it.

Clear the passage above it first with fishing line and compressed air.

 

Don't over think this.

 

You don't guess turns for the fuel screw, you turn it for max idle.

 

Read the 'how to set your pilot' in the jetting forum.

OK, good advice.  Thx.  I'll give it a shot and let you know.

[rpaitich]

OK, good advice.  Thx.  I'll give it a shot and let you know.

KoolAid:

 

Tiny holes in the pilot are clear; my pilot is stamped 52.  The manual calls the shorter jet, "starter jet"; it's 65.

 

You appear to the the go-to guy for this info; I found your posts from Mar 2012; nice and clear.  You've been productive, with 20,000 posts; thanks.  

 

I'm in Calif also (Sac area); do you have a business/shop?

 

My tuning project will be delayed by a while; I'll be out of the country for a few weeks.  I hope it's OK to reconnect when I get back, if needed.

 

Ron

[FORMA MOTO]

KoolAid:

 

Tiny holes in the pilot are clear; my pilot is stamped 52.  The manual calls the shorter jet, "starter jet"; it's 65.

 

You appear to the the go-to guy for this info; I found your posts from Mar 2012; nice and clear.  You've been productive, with 20,000 posts; thanks.  

 

I'm in Calif also (Sac area); do you have a business/shop?

 

My tuning project will be delayed by a while; I'll be out of the country for a few weeks.  I hope it's OK to reconnect when I get back, if needed.

 

Ron

A 52 pilot is no good

A 45 with a remote fuel screw, fresh slide plate seal and proper adjustmet of the fuel screw will get you all set

Choke and hot start plunger must be un-corroded and working

Stock 65 starter jet is fine for warmer climates

 

I am a low-voltage integrator, working from home.

I do have a showroom in my home

 

 

[RockerYZWR]

Those plants look very...medicinal.

[rpaitich]

Those plants look very...medicinal.

KoolAid,

 

Good "Showroom"

I expect we'll resonate on a few levels.  Including...

It looks like some good audio stuff.  I'm a EE/physicist by training/avocation, and enjoy the tech side of things.

 

Ron

[FORMA MOTO]

KoolAid,

 

Good "Showroom"

I expect we'll resonate on a few levels.  Including...

It looks like some good audio stuff.  I'm a EE/physicist by training/avocation, and enjoy the tech side of things.

 

Ron

Ron, yes.

 

Check these out. My hand-built speaker line from 1999:  Adiabatic-isothermal acoustic energy conversion via structural resonance and air baffling.....to eliminate sound reflecting inside the box and back through the cones and cabinet walls.....the subwoofer baffle is 5" thick...

The traditional cabinet face, which always puts the high frequencies forward in phase, has been stepped to provide an fully in-phase loudspeaker from 70 - 26khz.

The two woofers do not share any frequencies above 200 hz making it a hybrid 2.5-way speaker.

 

Edited February 22, 2014 by TheKoolAidMadeMeSick

[topcop45]

You can access the pilot jet from underneath through the drain plug on the float bowl.

I lay a small mirror on the cases underneath the float bowl and use a shorty screwdriver.

Takes 1 beer and 2 F-bombs and it's done.

Only 1 beer and 2 f-bombs? Takes a lot more for me!!!