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Dirt in the carb...not the airfilter.

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I read a post sometime ago, that stated that dirt is coming in around the throttle arm on the carb and not the aircleaner. I've been monitoring the intake tract on my X and it is always perfectly clean (white cloth swab), however when I pulled the top plate off the carb I can see a fine layer of dust around the slide chamber. If this is the source of the valve eating dust, does anyone have a fix??

Thanks,

Derik

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I'm not convinced that the dirt that accumulates in the carb

is getting in through the throttle shaft assembly.

I still think the micro particals of dirt are entering through the airfilter.

I noticed that my carb gets dirtier faster then my friends does, I have modified my air box.

His is stock, so I have created more air flow and I'm pretty sure that's why it sucks more dirt.

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I have had the same problem with dirt in the top of the slide chamber. It is not coming through the stock Honda air filter. I took off the plastic carb cover and it appears there is a blue plastic spacer on the shaft that would prevent any dirt from entering carb but cant say for sure. The vent hoses as I understand only equalize preasure and do not draw air into the carb. From the owners manual the carb diagrams of the hot start circut could be a source if it draws unfiltered air ?? However the dirt is getting in, it is doing some damage to the upper end. Honda need to address this since they claim dirt is the cause of the valve failure.

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Number 1, dirt is getting in my slide area and it is not coming from my air filter. Since my pump linkage cover is full of dirt, I assume it is coming from there, probably around the throttle shaft.

Number 2, dirt in the slide will definitely affect the engine and not do the valves any favors. Both the choke circuit and the hot start circuit draw air from above the slide, which is where the dirt accumulates. Plus, the dirt will just work it's way into the engine at all times.

The dirt appears to enter the linkage cover through the drain hole and around the throttle cables. Can someone explain to me why there is even a drain hole in this cover? :cry:

Dirt from the drain hole:

249376-PA034848a.JPG

Dirt entering around the cables:

249377-PA034846a.JPG

Slide Housing:

249378-PA034844a.JPG

Carb top cover:

249379-PA034843a.JPG

Slide:

249380-PA034845a.JPG

Now, I know a thing or 2 about filter maintenance and I am pretty damn sure there is no dirt getting past my filter. I have 7 Twin-Airs that I rotate through and I use a clean and fresh oiled one every ride. I completely saturate my filters wit Bel-Ray filter oil. My intake boot is spotless as is the bell on the back of the carb.

249381-PA034841a.JPG

I used some silicone-RTV and sealed up the linkage cover. I'll check it again afer a few hours and see if dirt is still entering the carb.

BTW, don't some years of the YZF's have a cast aluminum cover that seals up well as opposed to the chintzy plastic one Honda uses? :cry:

Also, my bike only has about 8 hours on it and this is the 2nd time I have cleaned my carb of this gunk. :cry:

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Excellent pics FGR!!! :cry: You have shown clearly that

vacuum around the throttle arm housing is pulling in the dust;or you ride in such a dusty area that it just settles inside the cover :cry:. I may try a smoke test to see if it draws smoke. We really need to eliminate this problem if we ever hope to see

our top ends last.

Derik

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The pictures are worth a 1000 words. Probably very few owners have ever inspected for dirt there unless changing needle. Even if you seal the drain hole I dont think the plastic cover is air tight. Thats alot of dirt on your slide.

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You can test for leaks with carb spray. Take the plastic cover off, start the bike, spray around the throttle shaft with carb cleaner. If there is a leak the motor will drop rpm, bog or sputter cuz the spray is inflammable. If the motor doesn't miss a beat you do not have a leak. It works on cars so it should work on bikes.

Has anyone considered that the gas tank is also a possible source for dust in the carb? The one way valve on the vent line does let air in. I imagine it would let fine dust enter the tank also. Especially if your not riding up front on those long dusty trails. I think I will stick a cigarette filter in the end of my vent line and see if it gets dirty.

Happy riding. :cry:

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Number 1, dirt is getting in my slide area and it is not coming from my air filter. Since my pump linkage cover is full of dirt, I assume it is coming from there, probably around the throttle shaft.

Number 2, dirt in the slide will definitely affect the engine and not do the valves any favors. Both the choke circuit and the hot start circuit draw air from above the slide, which is where the dirt accumulates. Plus, the dirt will just work it's way into the engine at all times.

The dirt appears to enter the linkage cover through the drain hole and around the throttle cables. Can someone explain to me why there is even a drain hole in this cover? :cry:

Now, I know a thing or 2 about filter maintenance and I am pretty damn sure there is no dirt getting past my filter. I have 7 Twin-Airs that I rotate through and I use a clean and fresh oiled one every ride. I completely saturate my filters wit Bel-Ray filter oil. My intake boot is spotless as is the bell on the back of the carb.

I used some silicone-RTV and sealed up the linkage cover. I'll check it again afer a few hours and see if dirt is still entering the carb.

BTW, don't some years of the YZF's have a cast aluminum cover that seals up well as opposed to the chintzy plastic one Honda uses? :cry:

Also, my bike only has about 8 hours on it and this is the 2nd time I have cleaned my carb of this gunk. :cry:

FGR: only 8 hours?!!!

That is a huge indictment right there! Seeing this much dust you would automatically assume that it has collected over a long period of time. But only 8 hours? That indicates that something is *seriously* wrong with a dust entry point somewhere on the carb.

BTW, I don't have our pics posted yet -- but we have *exactly* the same carb/dust pics as you show here. If anything our dust pics were even worse.

And yes, we have already gone through one RH intake valve. :cry:

Thanks for the post and the pics! :cry: - RandyB

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It would be great if we had a solid contact at Honda who would actually look at the evidence and help formulate a solution. It really bums me that a brand that I have bragged about for years is turning a deaf ear to the CRF Plight. I hope that Honda can lift its big ass up and help rather than duck around the issue and avoiding blame. I would be satisfied if I knew there was an effort being made, even if I had to pay for the solution to the problem.

Derik

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Slide:

249380-PA034845a.JPG

Considering the dirt is on the AIR FILTER side of the slide, the very fine dust is more than likely coming thru the filter. Twin air filters are more porous than stock. Speckles of light can be seen thru the filter when held near a bright light, unlike stock CRF filters. The suggestion that the throttle shaft is the source is difficult to evaluate. As mentioned above, the stock (restrictive) CRF250X owners have less of a "dirty" filter issue.

It would be interesting to know how the CRF250X carburetor lids would compare.

:cry:

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Considering the dirt is on the AIR FILTER side of the slide, the very fine dust is more than likely coming thru the filter. Twin air filters are more porous than stock. Speckles of light can be seen thru the filter when held near a bright light, unlike stock CRF filters. The suggestion that the throttle shaft is the source is difficult to evaluate. As mentioned above, the stock (restrictive) CRF250X owners have less of a "dirty" filter issue.

It would be interesting to know how the CRF250X carburetor lids would compare.

:cry:

Notice that the throttle shaft is also on the intake side of the slide. Also, the intake side of the slide has the open space behind it for the lifter arm as opposed to the front side of the slide which fits more closely to the body of the carb. Furthermore, notice how there is a clean circle where air rushing into the carb has "cleaned" the dirt off the slide. What all this adds up to is what to me looked like the dirt is first entering above the slide and then some of it is working it's way down the back side of the slide. That is how it really appeared to me when I disassembled the carb. Generally, there was more dirt in the very top of the carb (cover and body) and then less as you go south down the slide to the throat area.

As to suggestions about dirt coming through the filter or even the gas vent hose, I ride my CR250 two-stroke in the exact same conditions and with the exact same filter prep and never have so much as a spec of dust in my carb.

The first 2 hours on my bike were with the stock filter (albeit with extra oil added) and the filter screen in. I then installed the twin-air power-flo kit. It was then that I first opened the carb (to adjust the needle to match the removed screen). At that point, the carb already had dirt in the top. So I honestly don't think that the stock filter makes a difference. I'll have to check with some of my buddies with CRF's who still use the stock filter for comparison. But I am telling you, my air boot and carb bell are spotless. If this amount of dust was coming through the filter, you know you would see traces at the back of the carb, particularly at the air jet at the bottom of the bell.

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Yesterday I pulled the plastic cover and then lined the edges with a heavy grease to help seal. Also filled the drain hole at the bottom with a small piece of foam. I will ride thursday and then take carb apart to inspect for dust. I have been using the stock filter and still have the dust which is not coming through it. From the pictures it almost looks as if dust could be entering around the cover with the o-ring. Have you greased the sealing edge?

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......Considering the dirt is on the AIR FILTER side of the slide, the very fine dust is more than likely coming thru the filter. Twin air filters are more porous than stock. Speckles of light can be seen thru the filter when held near a bright light, unlike stock CRF filters. The suggestion that the throttle shaft is the source is difficult to evaluate. As mentioned above, the stock (restrictive) CRF250X owners have less of a "dirty" filter issue.

It would be interesting to know how the CRF250X carburetor lids would compare.

:cry:

After losing the RH intake valve... and replacing it... we went back to using the stock Honda air filter (backfire screen still in) with No-Toil. This combination (stock filter w/ Honda "branded" No-Toil) has been endorsed by Honda in a letter/response to another TT owner. We did this hoping to eliminate one of the dust entry "variables."

We are going to do one more dusty ride and then pull the top carb cover and check for "micro-dust." (Except that it's not "micro" at all...it's *real* visible...!) Will report back with what we find.

{Hey James, the wife *loves* her "new" bike with the JD Jetting Kit and Power Now -- it's really running strong now! :cry: )

Cheers! - RandyB

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FGR01,

Is there any easy way to clean the carb and seal the throttle cover without having to pull the carb?

Thanks,

Derik

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FGR01,

Is there any easy way to clean the carb and seal the throttle cover without having to pull the carb?

Thanks,

Derik

Only if you are a majician with the hands of a 1 yr. old :cry:

Seriously, it is so hidden behind the frame that I highly doubt it. Anyway, once you remove the plastic cover you will want to remove the top cover and slide as well and clean everything out good so you might as well just go ahead and remove the carb. I've done it so many times now that I can take off my seat, subframe, tank, and shock in no time!

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Could it also be that the modified airbox creates greater vacuum within the carb than unmodified? :cry:

Derik

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Could it also be that the modified airbox creates greater vacuum within the carb than unmodified? :cry:

Derik

Nope. We had the valve problem on the wife's completely stock 250x.

Bummer, eh... - rb

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Could it also be that the modified airbox creates greater vacuum within the carb than unmodified? :cry:

Derik

nope, just the opposite. The carb will pull from the area with the least resistance(assuming it has a choice), so a more free flowing filter makes the vaccuum in the carb lower.

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excellent thread guys!! the pics really DO say 1000 words. I really think a definative answer on this IS needed...and SOON. :cry:

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