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Goosedog

At wits end with dirt in the carb...help

41 posts in this topic

Ok here are the symptoms driving me nuts with my '02 426;

Every time I ride my jets get clogged, especially the pilot. I stop to pull off the catch bowl on the bottom of the carburetor and there's quite a bit of very fine dirt in there. I clean it out, blow through the pilot reassemble and go again....same thing.

Now here's what I've tried so far not knowing if the dirt's coming from the tank or the airbox;

Dumped out the tank, put in fresh gas (from another source) and added a fuel filter in-line between the tank and carburetor. Replaced the intake boot between the carb and engine and also the o-ring for the boot on the airbox side. Replaced the clamps for the boots on both sides. Got a new foam ring for the airfilter seal inside the airbox. And as always I service my airfilter properly after every ride.

My understanding is that for the dirt to be in the bottom of the carb it must be coming in with the gas, right? Anything from the airbox would just blow through the top to the intake I would think. Need some advice bad!

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I would say if its in the bowl then your getting it from the gas.

When I had my 426 I installed in inline fuel filter and my dirty carb issues went away.

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I installed in inline fuel filter and my dirty carb issues went away.

Thanks...but as stated above I've already done that and still the problem persists. :thumbsup:

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There will be a filter on the petcock inside the gas tank. Clean or replace that. It is also possible (but not likely) that dust is coming into your gas tank through the gas cap vent.

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There will be a filter on the petcock inside the gas tank. Clean or replace that. It is also possible (but not likely) that dust is coming into your gas tank through the gas cap vent.

Petcock filter and in-line filter are both in good shape. Even if dust was getting through the cap vent and past this redundant filter set-up how could so much be ending up in the bottom of the carburetor each time? I'm talking about every 4 hour ride, finding enough grit to say fill a contact lens.

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What kind of air filter oil do you use? I had a lot of dust in my carb when I used no-toil. I switched to PJ-1 and my carb stays clean.

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What kind of air filter oil do you use? I had a lot of dust in my carb when I used no-toil. I switched to PJ-1 and my carb stays clean.

No-toil.....but, is this not a contaminated fuel issue?

I can't figure out how dirt from the airbox can find it's way to the pilot jet. :thumbsup:

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Do you have filters on the carb vent lines? Kevin's Cycle sells a nice kit with one-way flow valves and filters...

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Check the vent tubes on the left side of the carb, they go strait to the bowl. I had the same problem on my 06.

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Could the dirt be coming from the carb vents? I never have understood how the vent lines have no filters from the factory. Maybe the hot start or choke seals leaking? I would think that one of those two would have driveability problems also--not sure though.

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Could the dirt be coming from the carb vents? I never have understood how the vent lines have no filters from the factory.
It shouldn't unless you have another problem somewhere. There should be almost no air flowing through those hoses under any normal circumstance.

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or your airbox boot is not sealing correctly :thumbsup:

Can dirt get from the airbox into the bottom of the carburetor? Can someone answer this conclusively so I could either rule it out or not. :p

Also I've just finished rinsing out my tank and spare gas can again (it was all clean). And while I had the petcock off I inspected the o-ring there and it was fine too, but I did put some grease on it as I re-installed it. When I held the in-line fuel filter up to the light however, I saw some very fine grit in the trap area. How it could possibly get past those petcock screens I have no clue, plus it didn't look like near enough to equal what I've been cleaning out of the bowl each ride.

Still puzzled. :lame:

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Can dirt get from the airbox into the bottom of the carburetor? Can someone answer this conclusively so I could either rule it out or not. :lame:

Also I've just finished rinsing out my tank and spare gas can again (it was all clean). And while I had the petcock off I inspected the o-ring there and it was fine too, but I did put some grease on it as I re-installed it. When I held the in-line fuel filter up to the light however, I saw some very fine grit in the trap area. How it could possibly get past those petcock screens I have no clue, plus it didn't look like near enough to equal what I've been cleaning out of the bowl each ride.

Still puzzled. :thumbsup:

Dirt will not pass through the inline fuel filter...fine particles will.

Check the sealing at the airboot

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Check the sealing at the airboot

I actually was just doing that and yes, there's fine dust inside the boot that must have gotten past the TwinAir. I can't figure this though because my procedure in airbox maintenance and filter servicing hasn't changed in years and this problem is new. I have for years, used No-Toil along with a foam rubber seal at the filter opening and never had problems before.

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A fine layer of dust on the air boot means one of five things:

> The air filter is too porous (airways too large), or not thick enough, or the air path through the element is too direct. This is not common with good filters, and very unlikely, to say the least, with a Twin Air.

> The filter is not sealing at the flange, the mounting post, or has a hole in it.

> The filter was not oiled thoroughly enough. Spraying oil on and calling it good doesn't get it. The entire interior surface (within the foam) must be coated with oil.

> The filter was not oiled heavily enough, or the oil is inadequate. The oil layer must be sufficient to trap all the dirt it comes in contact with and, hopefully, not just stick it to the wall or the airway, but completely wet over it. When this happens, the oil on top of the first dirt is able to trap more. Once all the available oiled surface is coated with dirt, we have....

> The filter was in use too long after the last cleaning and oiling, and the oil is now saturated with dirt to the extent that no more exposed oil is available to catch new dirt, or at least, too little of it is exposed to be able to catch it all. The length of time that is too long will vary based on what the conditions are where you ride, and on the 4 items above.

In reality, it's not possible to catch 100% of the very finest dust you're liable to ride through, and a very light layer of dust that almost can't be detected is acceptable, even if it's not ideal. Any more than that and you should try to find an answer to it.

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The dust you are fiding in your float bowls is most likely coming thru the vent lines. I had a nasty case of this very same problem with my 04 CRF250R back in 04. Drove me nuts until I figured it out.

What can and does happen, is that if the vent lines are positioned just so, they turn into venturis and air will be transferred from one side to the other of the bowl, and the dust will drop out in the fuel. The lines are plumbed to prevent this occurance, but it can happen anyway under the right circumstances such as addition of skid plates, etc.

Try snipping off a little of the vent hoses and/or shove a little old air filter up inside some of the lines.

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The lines are plumbed to prevent this occurance, but it can happen anyway under the right circumstances such as addition of skid plates, etc. Try snipping off a little of the vent hoses

The skid plate doesn't seem to be an issue, what are some other circumstances to create a venturi in the lines.

Also, what will snipping off a little line do to help?

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What he's referring to is caused by air flowing over the end of the vent line, and it's not a venturi, but it is a demonstration of the Bernoulli Principal. Positioning of the hoses has to be almost deliberate, because one of the vents has to extend into the under bike air flow at he right angle while the others are protected from it. Snipping the end off disrupts this.

If you are getting any dust up into the hoses this way, you should be able to see it on the inside of the hose as you look through it, unless yours are so old that they are no longer transparent.

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Tried all this, now we'll see on the next ride.

RTV siliconed the petcock to the tank and used red threadlock on the bolts. (There was a trace of dirt in that area.)

RTV siliconed the intake boot to the airbox.

Replaced neoprene filter ring in airbox.

New clamps on intake side of carb. (Trace of dirt there too.)

Snipped the vent hoses.

And probably most importantly....went back to oil-based filter oil (Maxima FFT) and no more No-Toil.

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