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willy_fitz

Crackcase Vent Hose Routing

11 posts in this topic

I had recently sucked up a bunch of muddy water and trashed the bottom end on my 08 WR450F. I am trying to understand the failure mode of how the mud got into the bottom end. Here is a picture of my airbox off the bike.

965444949_tqcbA-L.jpg

The current connection is beside the airbox drain plug and goes into the "dirty" side of the airbox. I believe this is where I got the ingress of mud into the crankcase. Since I have AIS removed I am thinking of moving the crankcase vent line to that location since it is higher and is also downstream of the filter.

Also, the airbox drain plug is just that, a plug. If any water or other junk gets into the airbox the only way out is through the motor. In the old days this plug was a one way valve and the water had a way to escape but I guess this is money saver for Yamaha just to shove a cap over the drain.

Any thoughts on this?

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you hit the nail on the head. move it to the top port. being on the bottom, it works as a funnel and anything that goes into the air box is now channeled to the bottom and that port is held under the water that is contained in the box. Put a vent cap on that lower port so water can drain out and you are not pulling mass amounts of shit into it and you will be good to go.

If this is a stock routing for the breather hose, I wpould be letting everyone know that they need to check it befor they get the same results.

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Yes thats the stock routing . isn't it stupid . I moved mine to the top port because I was blowing alot of oil out the vent at high rpm's . moving to the top port makes the oil run down the other tube back into the crankcase.

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Thanks for confirming my suspisions. Re-routing done & XR600 drain plug will replace the current drain cap.

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This sounds interesting and I think I like the idea.

Does anyone worry about pumping that oily crankcase mixture on the unfiltered side of the carb? Would that leave residue on the inside of the carb? Just curious.

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This sounds interesting and I think I like the idea.

Does anyone worry about pumping that oily crankcase mixture on the unfiltered side of the carb? Would that leave residue on the inside of the carb? Just curious.

On newer WR's any oil should drain back down the line coming from the starter gear housing and there will be no oil to spill over into the carb. Any oil that does spill over due to upset / whatever would be minimal and not worth worrying about when compared to sucking gunk into the bottom end which leads to very expensive repairs ($1500+). Your choice.

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You would have to submerged the bike over the seat for this to happen right? Assuming you didn't cut holes in the air box water can only enter through the airbox snorkel. Sounds like a pretty rare case.

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I have a 04 I put a T in the hose and cannot locate thin sidewall hose....all I find is thick radiator hose.

Any ideas?

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Any auto parts store should have some clear fuel line in bulk or prepackaged 3 - 6 ft lenghts. That is all I used off of the "T" .

(quote: - You would have to submerged the bike over the seat for this to happen right? Assuming you didn't cut holes in the air box water can only enter through the airbox snorkel. Sounds like a pretty rare case. : quote)

Most of us have removed the restrictive snorkel from the airbox and riding in wet conditions or even washing the bike can put water in the air box through the side vents and from the top of the rear fender as water and dirt run down the plastic. Alot of us use a vent plug from a Honda XR650 to go in place of the sealed plastic cap that is there or just cut off a small corner so water can get out. If this works it's item 18 in the Honda XR 650R airbox illustration

http://www.powersportspro.com/pages/parts/viewbybrand/7/Honda.aspx

Good Luck -- WR_Dave

Edited by WR_Dave
more info

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Any auto parts store should have some clear fuel line in bulk or prepackaged 3 - 6 ft lenghts. That is all I used off of the "T" .

Good Luck -- WR_Dave

I will give that a shot, thanks.

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I took a little different approach. I retained the stock vent location with the stock hose. I then found a rubber vacuum line of the correct O.D. that would slide in the vent hole from the inside of the air box. Push the line from the inside of the air box, with a little silicone sealer, until flush with the outside air box vent extension. Cut the vacuum line in the air box long enough to allow routing high and to loop the end down to prevent water from draining in. I've been through several deep water crossing with no water ingestion to the motor. As stated earlier, make sure that the drain will allow the passage of water and debris.

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