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Does the emulsifier tube wear?

14 posts in this topic

I've recently discovered I need a new needle as it's worn.

When I went into the local Yamaha dealer to ask about replacement costs (i've since decided to go with the JD kit after reading posts here) the mech also informed me I would probably need to get a new emulsifier tube.

Is this just a grab for more money or should both the needle and emulsifier tube be replaced at the same time? Does the emulsifier tube (which I must admit to having no idea about) wear as well? Bike's an 02 WR 426.

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I have to admit I have no idea what an emulsifier tube is? What part number is that on the schematic?...SC

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Isn,t That thing called a "Needle Jet"? If your needle is worn then you should probablly replace the needle jet since they were rubbing together.

You may want to search Needle Jet there may have been some discussion on how needle jet affects mixture.

You may also want to search the YZ forum since there has been a lot of talk on the ZIPTY carburetor mods latley (some of which may not apply to your carburetor.

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I have to admit I have no idea what an emulsifier tube is? What part number is that on the schematic?...SC

It's the first i've ever heard of it as well, which is what's got me stumped. Can't find reference to it in the manual.

Assuming the mech means needle jet, would that be included in a JD jetting kit?

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The needle jet is what would be called the emulsion tube in an automotive carburetor. It helps the fuel coming up the main jet mix with air to create a fuel mist and atomize as it enters the intake of the cyl. head. How did the jet needle get worn? Was the lock nut above the needle loose? If it was I would guess you need to replace the needle jet as well. First time I've heard of this problem , I must admit. Good luck getting a neelde jet from the dealer.:censored: !! WR Dave.

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If your replacing the needle you should replace the needle jet as well. IIRC it is not the attached to the emulsion tube. It should be two seperate pieces. This actually a fairly common problem, just not with this bike. I have replaced dozens of sets in various different street bikes. These bikes see much more use though. Also if youv'e ever looked at older honda (any of them) microfilm, the needle only comes as a set with the needle jet.

Symtoms of a worn needle jet are an overall rich mixture, and plug fouling if they're getting really bad.

Hell back in the 80's the 920 and i believe the 750 Virago ran hitachi carbs. When these needle jets wear out you can't get factory replacements and I'm not aware of any from thee aftermarket.

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My symptoms are almost exactly as you've described them. Around twelve months ago the bike started running really rough in the mid-range, to the point where sometimes I'd have trouble revving through to the top end. The plug indicated it was running very rich.

I contacted the local dealer who said, based on plug colour and my mid-range problem, that it sounded like a worn needle. He suggested I lean out the needle, so i moved the clip up one position.

It fixed the problem in terms of how the motor sounded and behaved, but the plug still looked a bit rich.

Just last week the bike started running rough again - same thing - moved the clip position and its fixed it, but it's only a band-aid fix. Going to properly fix it now with a new needle.

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If, as you guys indicate, it's not a common problem with this bike, maybe I should be looking for something wrong elsewhere rather than just normal wear and tear?

I don't want it happening again in a year's time.

Thing is, I've had the bike since late 02. It did 7000kms before this problem and now it's rapidly deteriorated over the past twelve months.

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Why don't you pull the needle jet out and take a look down it. The wear can be noticeable if you have a keen eye. Look for any ovaling in the oriface. Also if your bike has started runnig richer take a look at the little rubber seal on the choke plunger.

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I had a very similar problem with my 03 250f. My bike ocasionaly cold fouled plugs which was an inconveniance at first, but became a real problem as the fouling became more consistant. I cleaned my carb, adjusted the float level, changed to leaner jeting which helped at first, then the bike started runing rich at a quarter to half throtle. I changed the needle jet (emulsifier tube) all though I could not see any wear. The bike runs great now and has not fouled a plug since.

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My friend had this problem with his KTM 525. He just couldn't get the bike jetted right down low. It was always fat. He changed out the needle jet and it cleared things right up.

I'm experiencing the same problem where no matter how lean I went with the carb settings, it was still WAY fat. I've just changed out the tube to see if it fixes the problem, but I haven't ridden the bike yet.

One thing that I believe is the cause is a loose clip. I was using a clip that was extremely loose. I began having the jetting issues when I switched to the new clip. I believe the old clip allowed the needle to move within the jet and wear the jet. But that's just my theory and I have yet to prove that I've solved my jetting issue.

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The needle jet is what would be called the emulsion tube in an automotive carburetor. It helps the fuel coming up the main jet mix with air to create a fuel mist and atomize as it enters the intake of the cyl. head. How did the jet needle get worn? Was the lock nut above the needle loose? If it was I would guess you need to replace the needle jet as well. First time I've heard of this problem , I must admit. Good luck getting a neelde jet from the dealer.:censored: !! WR Dave.

I was able to order a needle jet from my dealer without issue. Part # on an '03 WR450 is 5JG-14947-00-00. My parts manual calls it Nozzle, Main.

Another symptom of mine was very poor gas mileage.

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Just fitted my new needle jet and the JD Jetting Kit my bike's never run so clean and crisp.

I discovered it was running waaaay too rich. I bought it second hand and have been happy with how it's been running (for the past four years) but haven't really messed with the jetting. I wish i had of now, heaps more responsive.

It was running a 180 main jet which, combined with worn needle was why it was running so rich.

Thanks for the advice guys.

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