# FAO Grayracer - Oil breather mod

I wouldn't, and the reason is that the breather outlet from the cam box in the YZF is not baffled in any way, and so is subject to exhausting more oil than the CRF.

Again, the best and simplest solution is just what Jones put up in the first place; a full size line running out and down with a T off the running to the air box. The downward line can't draw any thing up into the engine because the line from the air box will relieve the vacuum. Simple.

I think I will do this today. What size hose? He says 12mm ID, which is about, 1/2". Is that the best size?

I wouldn't, and the reason is that the breather outlet from the cam box in the YZF is not baffled in any way, and so is subject to exhausting more oil than the CRF.

Again, the best and simplest solution is just what Jones put up in the first place; a full size line running out and down with a T off the running to the air box. The downward line can't draw any thing up into the engine because the line from the air box will relieve the vacuum. Simple.

Yep.. very simple. The only thing extra to what Jones did is to slice the down line about an inch up from the bottom so that mud cant pack in the end (doubt it would..but easy mod)

I think I will do this today. What size hose? He says 12mm ID, which is about, 1/2". Is that the best size?
Convert 12mm to inches and ask that question again.
Convert 12mm to inches and ask that question again.

12.52mm is a 1/2". 25.4mm is 1".

12.52mm is a 1/2".
Not quite.

12.7mm is 1/2" ***

So its only .7mm difference between 1/2" and 12mm.

Im guessing it wont work cause the nipple on the head?

To continue with our little math exercise, 0.7mm is 0.028" (rounded). 12mm and 1/2" hose are functionally interchangeable.

I know that .7mm is very small difference, just makin sure.

Thanks for the math exercise.

I wouldn't, and the reason is that the breather outlet from the cam box in the YZF is not baffled in any way, and so is subject to exhausting more oil than the CRF.

Again, the best and simplest solution is just what Jones put up in the first place; a full size line running out and down with a T off the running to the air box. The downward line can't draw any thing up into the engine because the line from the air box will relieve the vacuum. Simple.

Gray, are you saying you wouldn't cap off the downline?

I think it'll be fine to reduce the drain line, and I made it very easy to remove in order to blow it out from time to time, just to make sure it doesn't plug...

What do you think?

Yes, I'm saying I wouldn't cap it off. I would not reduce it, either, but you could. If you route it as Jones did, the bulk of the air and oil flow runs through the down line as it normally would, but it's no longer capable of raising anything of any substance. By reducing or capping the down line, you force the bulk of everything to flow through the air box line.

Yes, I'm saying I wouldn't cap it off. I would not reduce it, either, but you could. If you route it as Jones did, the bulk of the air and oil flow runs through the down line as it normally would, but it's no longer capable of raising anything of any substance. By reducing or capping the down line, you force the bulk of everything to flow through the air box line.

Understood...I'll try it out, if it becomes oily at the air box I won't reduce the line...

Well, pulled it out to check it...Good news is no oil in the airbox...Bad news is the hose that runs to the airbox was being pinched because of the stretching to get over the T that I purposely got a little too big to avoid restricting the flow in any way...

Wow, this is the funniest thread ever...figured this out the hard way after finding water in my oil. Tip for flushing you get water in it. Change the filter, and change the oil run till warm. Drop the oil. I ran without a filter for a couple of minutes at idle between changes. (If you were like me you probably rode all day like this, 10min more won't kill you) It took 4 changes to run clear again. When dropping the oil tip the bike back and forth to move oil out of any crevices, a small amount of water will foul a lot of oil.

As for the mod. Here is a summary of what Grey is saying.

1. You will only suck up water when you are kicking the motor over.

2. The amount of dust you'll suck up is really nil.

3. A tee with 3" of hose running vertically will be all that you need. If you are in a puddle the hose will breath from the top, not the bottom.

4. You put the hose out the bottom to direct the mist of oil from the head to drip out the bottom.

If you paid more than \$10 bucks, and 10 min. Then you have too much money and time on your hands.

Pretty much what I said 6 months ago.

Since a filter isn't really nessesary unless you're in the airbox's dirty environment and since water will take the path of least resistance and because you want to keep the line's exit down low so oil won't drip down your engine...why not just leave the stock YZ configuration in place with the addition of a T and 3" of new line coming off the top of the exsisting breather line up under the tank?

That way (1) it looks stock, nothing wrong with that. (2) it now has an alternative port when the OEM line's under water. (3) no oil dripping anywhere but below the bike. (4) no line squeezed beside the shock that will eventually wear through.

2. The amount of dust you'll suck up is really nil.

I disagree...After a dune ride, or dusty desert ride take the breather off, and run a pipe cleaner through it...I don't know about you, but I get a lot of dirt, sand, and grime out of it...I think this mod is incredibly important to the longevity of the bike...

Have you done the mod where you run some pipe straight up?

Seems to me it may still have enough spitting force to eventually build up a mess where it exits...Guys that say oil can't drip up, are tripping, it's not like drops of oil, it's like a fine oil mist, if it didn't spray up it wouldn't have gotten into the tube in the first place...And they are also assuming the bike is staying straight up...I've gone down where the bike is basically upside down on the side of a hill...Maybe with straight pipe it would've leaked oil right through the cam box, and out the straight pipe, all over the fuel tank and motor, in the sand...No thanks...I'd much rather have it have run through the air box...I'm doing mine a little differently, will post pics later, I think I've got a good setup now...

Yes, I've spent \$10 on various pieces and too much time trying to come up with a good way...But I believe it contributes a little bit for others as well (if it works out)...And be sure that guys who work for the big 5 lurk these pages for ideas to contribute to future bikes...

I'd make a bet Yamaha will route that breather differently sometime soon...

OK...I used pvc fittings which the hose fits into so the flow is not constrained at all like the T they fit over...Used plastic/rubber epoxy for a tight seal...The fittings were white so after I epoxied the hoses I sprayed the fittings with high temp silicone spray...

I disagree...After a dune ride, or dusty desert ride take the breather off, and run a pipe cleaner through it...I don't know about you, but I get a lot of dirt, sand, and grime out of it...
I don't. I've never found anything in any of mine but oil residue. And that's in the Imperial County Desert, where all of the dust in California comes from. Some of our dust is fine enough to be considered a gas.
I don't. I've never found anything in any of mine but oil residue. And that's in the Imperial County Desert, where all of the dust in California comes from. Some of our dust is fine enough to be considered a gas.

I guess it's mostly just sand from the dunes then, mixing with the oil, appearing to be dirt...After those rides I'm pulling sand out of my ears for weeks, lol...Trust me, the sand is stuck to the oil in that tube...I had to run a pipe cleaner through it before doing the fix, and did get a decent amount (ok a lot is an exaggeration) of gunk out...

The bottom of the tube is filthy, of course, but the the top 4" is clean.

This hasn't been the case for everyone, of course, but if you observe a few simple cautions you can generally stay out of trouble pretty easily.