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Crank case filters

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I have heard from a mechanic that it is a good idea to put a filter on the crank case vent on the YZF's how many of you guys are doing it? And what set up did you go with? I have thought about one of those K&N filters like I have on my street bike (about 1.5 inches in diameter and about 1 inch tall) but I am not sure the K&N will stand up to much harsh riding since it is made of cotton. Any ideas would be appreciated.

Thanks

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Re-route it into the airbox...

You can then choose whether to add a filter or not to it.... prob not need it.

------------------

--

**Ride it like you Stole it!**

Matt Porritt

99 YZ400F

Rubber Chicken Racing

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Matt,

What do you do about the spooge that drools out of the vent? Do you just wipe it out during filter changes or does it run down onto the shock and swingarm? I never thought about relocating it, but if it sucks water or mud then maybe I will. Thanks

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ETS,

It DOES suck water, mud, sand, whatever it can get. This was a hot topic on the WR websight. One guy sucked a butt load of sand into his engine - Massive damage. It sounds as if the engine sucks while it is being started. When it is running, the case is positively pressurized and the tube blows. One guy mounted a PVC valve to ensure air does not get drawn in while kicking it over. I have ridden in very deep, muddy water and have stalled out several times. Upon tearing down my top end, I have found several score marks, one bad enough to warrant replacing the cylinder. I do attribute it to this bogus phenominon. That will be this fall after the big ThumperTalk Moab, Utah trip.

------------------

99 WR, all YZ mods, de-octopused, OEM YZ tank and seat, jetting by Clark.

Moab bound for 2000!!

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I put a k&n fiter on the hose of my YZ250f and put it in my air box.

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Here's what I did:

1. I cut the hose at the front of the valve cover where it goes down the frame

2. Installed a 1/2" brass tee and ran the stock hose down and another hose up and zip tied it to the oil tank breather hose

3. Installed a 1/2" 90 degree barb to thread fitting on top hose to face the open end down about 45 degrees(to keep junk out). Also cut a piece of air filter and stuck it it the thread end of fitting

This way, if you do have to start your bike in water, there is no vaccuum present at the bottom stock hose because of the open top end. Unless you're completely submerged and then you're screwed anyhow! Also, any oil that will be blown out will still go down the stock tube and not make a mess of your airbox or wherever you put it.

[This message has been edited by akg800 (edited 03-09-2001).]

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Could someone explain why crankcase pressure or vaccum would affect the operation of the oil pump? Is it a pulse-pump or a traditional orb-pump/gear pump? A gear or orb pump should not be affected.

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If the oil pump icounters abnormal presre it will hinder oil flow.

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I think that a pcv valv would not be a good idea I would not want the oil pump to incounter any abnormal presure and hinder oil flow. All I did was put it in my air box I have no oil in my air box. And yes it will stand up to harsh riding. This is the best idea doun't try any others. :)

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Keep in mind that there is a piston moving up and down inside of the crankcase. As the piston travels downward, it pushes air/oil vapor...etc ahead of it and needs to be vented so that gaskets and seals don't encounter a tremendous pressure pulse. Try this, the next time you start your engine, put your finger tip at the end of the vent tube and you can feel those pusles. They are pretty strong. Try to imagine what would happen it these pulses were not vented.

AKG: I like your idea. Might I had one small addition? Suppose that instead of a "T" connection, a "Y" connection was used. It would serve the same purpose as the "T" with one exception. The top right side of the "Y" would assist gravity in keeping the oil going downward. It might also make routing a bit easier.

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Boit that is a very good idea with the y idea that way the oil would go back in the motor and not out the vent.

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YZMan: Thanks for the comment. However, I think you misunderstood what I had in mind. This "Y" connection would be not make oil drain back into the engine. Any oil that's vented never gets back into the engine. The reason for the "Y" is that it would ensure that most of the vented oil goes downward to the bottom tube to the ground and not through the tube that's routed rearward where it would spooge onto the frame or inside the airbox...depending on where it is ultimately routed. Sorry for the confusion.

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YZMan: Thanks for the comment. However, I think you misunderstood what I had in mind. This "Y" connection would be not make oil drain back into the engine. Any oil that's vented never gets back into the engine. The reason for the "Y" is that it would ensure that most of the vented oil goes downward to the bottom tube to the ground and not through the tube that's routed rearward where it would spooge onto the frame or inside the airbox...depending on where it is ultimately routed. Sorry for the confusion.

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