FAO Grayracer - Oil breather mod

I think what Goosedog suggested makes perfect sense to me. Just add a T higher up on the hose with a little stub piece coming off it. All you really need is a way to break the vacuum that is created. I plan on trying this method. The only drawback I could see is if oil does come out the higher opening.

I think what Goosedog suggested makes perfect sense to me. Just add a T higher up on the hose with a little stub piece coming off it. All you really need is a way to break the vacuum that is created. I plan on trying this method. The only drawback I could see is if oil does come out the higher opening.

The only way oil's gonna come out the higher hose is if your bikes upside down. I haven't done this mod yet but I think in addition to what I described eariler, I will put a small filter on the upper hose just to keep any dust out.

Think of the mess to deal with when you have to take off the carb.

I performed this mod to my 99 WR 400.

The real mess was the destruction of my cam :lol: journals.

$400.00 later, I realized a better method was in order than the stock :worthy: setup...

I performed this mod to my 99 WR 400.

The real mess was the destruction of my cam :lol: journals.

$400.00 later, I realized a better method was in order than the stock :worthy: setup...

What did the damage? Dust coming in the stock breather tube? Water from a river crossing?

What did the damage? Dust coming in the stock breather tube? Water from a river crossing?

I stalled my bike in a puddle of water over the lower frame rails.

This was back in 1999 when the level of knowledge of these Yamaha's was almost non existent...

(which is why the original TT owner started ThumperTalk >> to learn about the WR400)

Goose, if you get to this mod before I do let me know what kind of filter you go with.

I stalled my bike in a puddle of water over the lower frame rails.

Crap, that's exactly what happened to me and I've flushed about 8 qrts of oil thru the bike now and have finally gotten the water out. How will I (or did you) know if I/you damaged the cam journals or anything else, short of an engine tear-down?

Goose, if you get to this mod before I do let me know what kind of filter you go with.

Wiil do. :lol:

How will I (or did you) know if I/you damaged the cam journals or anything else, short of an engine tear-down?
The other possible ways are:

  • X-Ray Vision
  • Psychic Powers
  • Omniscience
  • Wild, Lucky Guess
  • Denial

I think what Goosedog suggested makes perfect sense to me. Just add a T higher up on the hose with a little stub piece coming off it. All you really need is a way to break the vacuum that is created. I plan on trying this method. The only drawback I could see is if oil does come out the higher opening.

Allright, here is the answer. Run the stock set up. Simply cut the tube and put in a "Y" connector with a short piece of tube. This way it can't drip upward.:lol:

How will I (or did you) know if I/you damaged the cam journals or anything else, short of an engine tear-down?

The engine stalled while idling, and I was thinking, "Huh...???"

I pulled the valve cover and saw the dirt on top of the head >> pulled the cam caps >> saw the journal surfaces damaged...

Allright, here is the answer. Run the stock set up. Simply cut the tube and put in a "Y" connector with a short piece of tube. This way it can't drip upward.:lol:

You took the words out of my mouth, I was just out lookin at the bike and the same thought crossed my mind.:worthy:

How about plugging the lower leg and drain it occasionally? That way there is no way to suck up water/dust.

that will cause the blow out to happen somewhere else, that line does see pressure/vacuum under certain conditions...

that will cause the blow out to happen somewhere else, that line does see pressure/vacuum under certain conditions...

If you did the mod and have a tee with a filter in your airbox, then that is where the vacuum/pressure equilizing will occur. This way you control where it vents while still providing a place for condensating vapors to collect.

Just my 2 cents

I stalled my bike in a puddle of water over the lower frame rails.

This was back in 1999 when the level of knowledge of these Yamaha's was almost non existent...

(which is why the original TT owner started ThumperTalk >> to learn about the WR400)

Did you kick the bike when stuck in the water? That would cause the water to suck into your engine. I would have gotten my feet wet and pushed the bike :p out of the mud/water hole.

How about plugging the lower leg and drain it occasionally? That way there is no way to suck up water/dust.
If you did the mod and have a tee with a filter in your airbox, then that is where the vacuum/pressure equilizing will occur. This way you control where it vents while still providing a place for condensating vapors to collect.

Just my 2 cents

I think he was talking about not doing the mod and just plugging the hole...

$70?? I'm in the wrong line of work.

Anyway, locate the two vent lines that exit the float chamber pointing straight up and route them to either the air box or up under the tank. Some run filters on them, I don't. The only time there is a steady, continuous vacuum applied to these hoses is when running the "choke". Air for that circuit comes from the float bowl, and must enter through the vent lines. (bad design)

Grayracer, Do you think that the lack of vacuum from a check valve would have ill effects on a YZ motor??

....also the two vent line exits on the carb that piont strait up are on opposite sides of each other on the carb. Are those the right ones?

You mean the vacuum caused by the check valve? No.

On the vent lines, yes.

If all that's needed is a check valve, wouldn't a PCV valve from any auto store fit the bill? They come in all shapes and sizes.

You mean the vacuum caused by the check valve? No.

Well, because the engine breaths in and out from that valve cover hose. Will the check valve being inline, and not letting the minimal inhale enter the engine cause any problems?? Because that all i was going to do; just go get an appropriate PCV at the auto parts store.

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