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05' WR450 hesitant below 1/3 throttle

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Alright, I've searched and searched and tried things and nothing seems to resolve the running issues on my 05 wr450. Hopefully someone can help.

I bought the bike and it seemed to run fine but honestly only rode it once around on the street.

The bike came with a somewhat gutted stock muffler, grey wire mod and also the throttle screw mod, it has the following jetting:

main: 168

Pilot: 48

Starter jet: 65

Leak jet: 40

Needle: markings are GDDT R, with 7 positions (currently at the 5th from the throttle valve side)

Fuel screw: seems to run best around 2 turns out.

Then I installed a baja designs kit for street legality with the stator mod etc.

It runs a little funky at part throttle. It wasn't too bad around 500 foot elevation (still has issues though) but then I took it up to about 4000' and it got worse. Anything from about 1/3-1/2 throttle up it feels GREAT, but anything below is pretty boggy and it hesitates. So since it got worse at elevation I figured it was a fueling issue. So I tried moving the needle up 1 and then 2 clips leaner (from 3rd to 4th and then 5th) and made no difference. Then I tried the pilot jet down to stock 45, seemed to run worse and still ran crappy at 3 turns out on the fuel screw. I notice it lot too if I'm at a stop on a hill and I try and slip the clutch, it just bogs down and wants to die.

Any thoughts? Spark plug was replaced about 100 miles ago. The bike apparently only has about 500 miles on it in total, seems like a fresh motor to me.

Currently I've got the carb apart again, to give it a thorough clean/inspection. I've also tried draining the gas multiple times thinking it was bad gas, no difference. The stator puts out about 13.5 volts at idle and when revved up. The battery is pretty much toast, but it will kick over and start just fine. Was thinking maybe the battery could be hurting things but as long as the charger is putting out enough juice seems like it shouldn't matter. I also tried unplugging the TPS sensor as I've heard people say those things can cause problems at steady state cruising conditions ...and it made no difference.

PLEASE HELP ME!

Chris

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Billions of posts on the subject. It's all in the pinned post at the top of the forum. Your jetting is mixed up, and you have not de-regulatehed the carb. The stock ignition has a problem that is most easily solved by disconnecting the TPS. Your bike is currently very RICH below 1/4 throttle....

45 pilot*

100 pilot air jet*

160 main jet

stock power jet, main air jet

NCVS needle on 3rd clip

*Remove / disable the ACV system

Remove the Air injection system

Remove any air box intake restrictions

Remove any exahust restrictions, but really you need a straight through pipe for best results.

-- Your carb is 12 years old. It needs to be pulled apart and serviced. The pilot jet passage will have corrosion in it that must be reamed out. Put in a NEW pilot jet.

The needle jet and slide plate seal must be replaced due to wear. An R&D fuel screw is needed for pilot tuning.

 

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Which post are you referring to specifically I have looked through all of the ones pinned at the top. 

I'll clarify that I have the AIS removed, airbox snorkel removed, fuel screw installed for easy adjustment and a stock 80 pilot air jet.

Based upon the jetting database most people are pretty close to what I have as a setup and they seem to be happy. So I feel like I'm not way off here? Thinking maybe I have an ignition problem...I still have yet to try and calibrate the TPS sensor.

I've got the carb apart right now and the pilot jet and passage below look spotless, I blew them out with air anyways but using lights and a magnifying glass they are showing shiny metal surfaces.

As I said before I've run with the TPS disconnected and notice no difference.

If my bike is very rich below 1/4 throttle then how come going to a leaner 45 pilot jet made it no better, actually made it run crappier.

Needle jet looks good too, what exactly is the slide plate seal, does that attach onto the face of the throttle valve?

I got a new battery coming on Thursday so will give that shot and report back.

 

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Replace the emulsion tube / needle jet while you are in there, as it ovals and makes strange rich conditions.

 

You have to be more specific about your symptoms: rpm, throttle position, running quality, to get specific advice.

The stock stator is fragile, and can go bad especially if the bike was run with the stock jetting for a while (over heats).

Using a service manual, test the stator cold and hot for issues.

The TPS should be unplugged. If it is left connected you will experience a 'studder' at partial throttle at low rpms.

The carb has an Air Cut Valve, that will remove any decel popping due to the AIS system. If the AIS system is removed, the ACV should be by-passed.

This requires a 45p, and a 100 pilot air jet, and blocking off the ACV passages by removing the white floating piston and making a gasket that covers everything under the cover, and re installing the cover. 

Once it is bypassed, you can get better fuel screw tuning results.

 

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As for symptoms the bike overall doesn't run real horrible but its very annoying and is easy to kill when taking off and is not very stable/responsive during low rpm and low throttle input riding. It seems to be mainly noticeable at low rpms (no tach here but guessing below 4000 rpms) but really anything part throttle, maybe 1/8 to 1/4 throttle is quite unstable. 1/2 throttle to full throttle the bike pulls real nice, no issues whatsoever.

Last time I had it warmed up and running I was able to get it to stumble just off idle, by barely cracking the throttle open, and I could hold it there in the stumbling state, and more throttle didn't seem to do much, I also tried adjusting the fuel screw while holding it in this stumbling state and did not have any affect on the engine. It idles just fine and starts fine too, seems to like two turns out on the fuel screw give or take.

I'm puzzled myself, doesn't appear or smell like its running rich? 

Do these things eat plugs very much? I used to have to change my plugs quite often on my FZR600 but the one I put in only has about 150 miles on it.

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Plugs last for years.

Your symptoms are typical of a carb that is only partially upgraded to the necessary specs, and with worn out parts.

You cannot adjust the fuel screw that way.

You get the motor hot, set the fuel screw at 1 turn out and adjust the idle as low as it will go. Then raise the idle with the FUEL SCREW. 

Once the idle is as high as it will go with the fuel screw, with no additional turning past that point, adjust it to the correct idle withe the idle screw, if needed. 

Now go back to the fuel screw and turn it very slowly, listening for the smoothest and highest idle. It is VERY SUBTLE, but that is how you find the correct turns out.

 

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Any recommendations on where to get new jets? Should I just go to a local dealer, or is there a good online place anyone recommends?

Last time I toyed with the fuel screw (and yes has a brand new o-ring) it really didn't seem to have much of an affect on idle until I was closer to 1/2 turn out or up high around 3.5 turns out, in between there even revving and letting it settle doesn't seem to make much difference on the idle speed when you turn it 1/4 to 1/2 turn at a time.

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40 minutes ago, 206danebmx said:

Any recommendations on where to get new jets? Should I just go to a local dealer, or is there a good online place anyone recommends?

Last time I toyed with the fuel screw (and yes has a brand new o-ring) it really didn't seem to have much of an affect on idle until I was closer to 1/2 turn out or up high around 3.5 turns out, in between there even revving and letting it settle doesn't seem to make much difference on the idle speed when you turn it 1/4 to 1/2 turn at a time.

It is subtle.

Jetsrus.com

Sudco

Jd jetting

Any jap dealer

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Was checking out the ignition system today, spark plug looks pretty good, gap is good. The primary coil Resistance looked good, but the secondary at first measured open circuit. I came back 10 minutes later and kinda tapped on/pulled on the coil and then the measurement was fine at 5.5K ohms... weird. I'm wondering if this thing is on its way out... now I can't get it to measure open circuit, anymore, really weird. I definitely was measuring properly beforehand too, I was scraping all along the inside of the spark plug end to get a good connection and nothing, just open, and even checked the resistance to the leads themselves to ensure the multimeter was good.

I think I'm gonna replace regardless, any thoughts on where to get one other than the dealer?

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So I have been reading a lot about the CDI related stutter/hesitation in the forums, are people still using these new CDI's? This sounds very much like my problem. I couldn't find a direct model on the Vortex website for an 05' WR450 but was able to get an email confirmation from Dynatek @ $380! ouch.

Krannie, Are you using a different CDI than the stock unit?

 

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1 hour ago, 206danebmx said:

So I have been reading a lot about the CDI related stutter/hesitation in the forums, are people still using these new CDI's? This sounds very much like my problem. I couldn't find a direct model on the Vortex website for an 05' WR450 but was able to get an email confirmation from Dynatek @ $380! ouch.

Krannie, Are you using a different CDI than the stock unit?

 

Yes I did.

I have a used one for sale if you are interested.

PM me.

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