Dirt in the Carburetor


14 replies to this topic
  • 42A

Posted April 02, 2012 - 06:44 AM

#1

I have an 07 WR450F and I can't seem to be able to keep dirt out of the Carb........a very small amount but enough to cause a problem over time. I know that some of the first 07's had a hole in the center of the filter cage, but that isn't the case with mine. I clean the filter and do my best to make sure that it's sealed, I've tried two different filters (Uni & K&N) but I still have a small amount of dirt in the bottom of the float bowl after every ride. I just pulled the air box out to see if there is any way dirt can be getting in, but haven't been able to find a leak.
Is there something that I'm missing or should know? Thanks

  • grayracer513

Posted April 02, 2012 - 06:49 AM

#2

Dirt in the float bowl comes in either from the tank, or through the vent hoses while the choke is being used. For the most part, very little of what flows through the main air stream will ever find its way into the bowl.

  • 42A

Posted April 02, 2012 - 07:12 AM

#3

I've just installed a new IMS tank and filter, so i know that isn't the problem. I guess the next step is to install a vent hose filter. Thanks

  • harvmushman

Posted April 02, 2012 - 08:09 AM

#4

There is a different option. It adds to what the knowledgable Grayracer said about the vent hoses. It can happen at times other than just running the choke. I don't know how, exactly, I just know that it happens.
The only place I have had it happen to me in a regular way where there was a noticeable collection of dirt particles is in the fine silt and sand of Baja _ where prolonged riding through lots of this stuff is the norm.
There are other older threads here on TT where dudes talk about it. It is a phenomonon with the FCR carbs, and first came up with Baja dudes and the XR650r.
The fine silt can migrate up the vent hoses and collect in the carb. A friend and I had enough collect in one Baja trup that it filled up the carb drain deals on our WR450s. His pilot jet clogged.
The intake tracts on both bikes were spotless. We both were using TWO fuel filters, including a Pingel in-line filter.
The only option left after we inspected everything was the vent issue. We both bough filter kits for our vent hoses (there are a few options) for our Baja bikes and have not had the problem since.
Now, I ride and race a lot in Montana _ in a lot of different conditions. And I have only ever had a TRACE amount of dust collect in the top of the carb's vent slide from this issue.
So it seems to me that it really requires some very specific conditions for a significant amount of dirt to get in the carb from the vent hoses.

  • zlathim

Posted April 02, 2012 - 08:19 AM

#5

mgouras- Great tech. Thanks for posting!

  • 42A

Posted April 02, 2012 - 08:45 AM

#6

Thanks guys for the input, The more I think about it, it also might be that the dirt is being sucked up through the breather hose that connects at the bottom of the air box and from there to the carb and then to the valve cover. Out of all the bikes Iv'e had over the years, I've never had one that collected so much dirt, that's why I thought I'd ask TT, I figured that out of all of the guys that had WR450's someone would have had the same experience ...............I'll do some more checking.
Thanks again.

  • Krannie McKranface

Posted April 02, 2012 - 11:33 AM

#7

Every time you start or stall the motor, you suck air up those hoses. Filter them.....!

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  • GlennR

Posted April 03, 2012 - 04:26 AM

#8

Every time you start or stall the motor, you suck air up those hoses. Filter them.....!


How do you filter them? Do you have a name or part # of the filter, or a photo ?

Btw, I've noticed that my vent hoses drip fuel when I lean the bike over. Is there a way to prevent that ? Seems "wasteful" when I'm miles from gas to watch it pour out. :thumbsup:


thanks,

  • MANIAC998

Posted April 03, 2012 - 04:37 AM

#9

Glen, There is no way to stop the vent hoses from leaking fuel when the bike is leaned over, it's one of the things they are supposed to do! They let air into/out of the float bowl area so that fuel can flow into the bowl. You can lessen it though, by making sure your float heighth is set perfectly as per the manual. I've even known some that will go so far as to run even less float heighth than the manual requires, which in turn would lessen fuel leakage even more, but will require complete rejetting of every circuit in the carb. This is due to the fuel having to travel higher up each passageway, due to the lower fuel heighth. Maniac

  • GlennR

Posted April 03, 2012 - 05:40 AM

#10

Glen, There is no way to stop the vent hoses from leaking fuel when the bike is leaned over, it's one of the things they are supposed to do! They let air into/out of the float bowl area so that fuel can flow into the bowl. You can lessen it though, by making sure your float heighth is set perfectly as per the manual. I've even known some that will go so far as to run even less float heighth than the manual requires, which in turn would lessen fuel leakage even more, but will require complete rejetting of every circuit in the carb. This is due to the fuel having to travel higher up each passageway, due to the lower fuel heighth. Maniac




I'd think you could just run longer hoses up (above the carb) and loop them back down. That would allow them to breath, but the fuel wouldn't pour out nearly as easily. Sort of a "dry P-trap".

I'm sure it's not that simple...or is it ?

Also, maybe a dumb question, but why are there so many tubes ? I think there are 6 of them.

  • MANIAC998

Posted April 03, 2012 - 03:40 PM

#11

Sadly, no it's not that simple. If you were to do that, then fuel would get trapped inside the semi-circle, and the next time the floats lowered then the fuel in the hose would get in the way of allowing air to compensate for the drop of fuel in the float bowl. And since fuel doesn't flow the same as air, I think you would have some serious tuning issues. Along the same line of thought though, you could build a catch-can whereas the fuel would dump into the catch can to be used later. Is this really an issue though? Are you really needing every drop of fuel so badly that your going to build some Rude Goldberg device? Or wouldn't it just be easier to use a larger fuel tank? ManiacNov 23,2011 006.JPG

  • SilvFx

Posted April 03, 2012 - 05:26 PM

#12

How do you filter them? Do you have a name or part # of the filter, or a photo ?

Btw, I've noticed that my vent hoses drip fuel when I lean the bike over. Is there a way to prevent that ? Seems "wasteful" when I'm miles from gas to watch it pour out. :thumbsup:


thanks,


7602racing dot com is one company that makes and sells them.

There may be others......just this company came to mind. No affiliation and no endorsement (I have never used them).

  • GlennR

Posted April 03, 2012 - 06:20 PM

#13

I just read that tracks require racers to have sliders and catch cans to protect the pavement. You'd think the fans would appreciate a little fire along with their crashes. . :thumbsup:

7602racing dot com is one company that makes and sells them.

There may be others......just this company came to mind. No affiliation and no endorsement (I have never used them).



Good to know, thanks.

  • n16ht5

Posted April 03, 2012 - 06:27 PM

#14

does anyone route the secondary vent lines into their air boxes?

  • 42A

Posted April 04, 2012 - 08:57 AM

#15

Thanks GlennR for the link to 7602Racing.com,

I'm going to order the carb. filter today, and hopefully that well cure my problem.

42A




 
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