Would not have a crankcase breather filter have a negative affect?

[pnedac]

On performance? I see on my XS 650 that there looks to be a splitter coming out of the top. Wioud I need two lines and filters? I know, dumb question probably, but I want to put something on it if there is supposed to be something there you know?


Thanks!

 

[tonyc]

Pnedac you can run a "T" and use one filter if you like. I run two myself.

 

[5twins]

There were different set-ups depending on the year. Some years capped one side of the "Y" and ran just one hose. Others ran two hoses but with reducer plugs in them. If you don't have those reducer plugs and run 2 hoses, too much vapor can blow out. If you don't have them, I would cap one side and run one hose. To reduce the amount of vapor and oil lost out the breather, Yamaha eventually changed the housing to a single outlet with a very small outlet hole. You can swap that late style housing on if you like.

 

[jefft]

Seems like thats what many have done. Lots of double outlet breathers on ebay, not so many singles.
jefft

 

[hooktool]

That's because there were way more double ones made.

John

 

[pregrid]

Um, yeah................

 

[Mollard]

My 75 has the y with two hoses, maybe 1/2"? Maybe to much? I think they are stock....

 

[Patches]

If the bike I'm building has a Y-style; I cap one of them as having two is redundant. There is no need to run two breathers/hoses/filters.

 

[bluebikerblan]

I assumed that the breather vent line was divided into two lines in order to feed two divided but similar vent streams into each air box and carb. You know....like who would want only one gummed up and oily CV carburetor slide?

But.....yes a crankcase breather vent to atmospheric pressure is needed for a number of reasons. Blue

 

[ProSimex]

I run the tube down to my chain, free lubrication. ( I still hit it with the proper stuff now and then though)

 

[dickymo]

I hope I dont step on anyone's toe's here but Ive been reading up on breather mods until im blue in the face.
Ive been looking for a thread on how to modify the dual outlet style of breather box that most of us seem to have in order to find a solution.
According to what ive read there is really no need for both outlets, on this type of breather box so why not make the dual outlet into a single outlet?
I was thinking that a guy might be able to, in theory anyway, take the double hose breather box such as on my 77, cut off the two nipples, just enough as to get a flat working surface.
Hopefully this would leave enough material to allow tapping into the housing with a 3/8" or 1/2" npt tap which ever fits best, and attach a 90deg elbow for a single hose setup.
It all sounds so simple, it just cant be that easy, or can it?
Has anyone out there tried this?
Dose anyone know what mechanical implications might be involved?
I know this would not improve performance by any means it would only allow for less clutter between the carb's, and hopefully allow a bit more room for carb maintenance.

 

[jayel]

I hope I dont step on anyone's toe's here but Ive been reading up on breather mods until im blue in the face.
Ive been looking for a thread on how to modify the dual outlet style of breather box that most of us seem to have in order to find a solution.
According to what ive read there is really no need for both outlets, on this type of breather box so why not make the dual outlet into a single outlet?
I was thinking that a guy might be able to, in theory anyway, take the double hose breather box such as on my 77, cut off the two nipples, just enough as to get a flat working surface.Hopefully this would leave enough material to allow tapping into the housing with a 3/8" or 1/2" npt tap which ever fits best, and attach a 90deg elbow for a single hose setup.
It all sounds so simple, it just cant be that easy, or can it?
Has anyone out there tried this?
Dose anyone know what mechanical implications might be involved?
I know this would not improve performance by any means it would only allow for less clutter between the carb's, and hopefully allow a bit more room for carb maintenance.

no need to cut it, pretty sure it's just a pressed in fitting, twist it out and the hole could be tapped for a pipe thread fitting

 

[dickymo]

Thanks jayel! ill give it a look manana and see if I can indeed yank the dreaded two headed transplant out of there.
After I posted the previous I ran across a build thread by thelowlife that had apparently done what you suggested, and installed what looks like one of mikesxs breather valves.

 

[XSLeo]

On my 75 it has one of the nipples plugged, the other is open. I put on about 2 inches of the stock style hose, the 80190 HELP power brake chack valve, about 18 inches of 3/8 hose from the valve, down behind the engine.
This is almost how it was stock. Stock didn't have the valve.
Yamaha knows two strokes. They never built a four stroke before the 650's. They knew just how much crank case vaccum and pressure worked in a two stroke.
When they built the 650 they wanted to eliminate as much of the crankcase vaccum/pressure they could.
At first they used two nipples and hoses. To much oil blowby. Cut back to one hose, still too much adsjusted oil level, still too much.
They tryed resticters in the nipples. They went with the single nipple breather box, even added restriction. At this point the ran the hose to a tee and linked them into the stock air boxes to be EPA compliant.
They got it too small and started getting seal failure. This was at the end of the run, and they stopped production in favor of the four cylinder engines.
As far as a filter the length of hose was all that is needed. There will be some oil blowby, thius oil coats the inside of the hose. As the cylinder breaths air out and in this coat of oil traps any thing that comes back in.
Myself if I had one of the later one nipple caps I would drill it out to 5/16 or 3/8 inch, use a short hose , the check valve and let it point at the air filter. Or run a hose down below the engine. The two nipple just plug one side, run the same as a one nipple.
If you want a filter on the end then put one on.
Leo

 

[jefft]

XSLeo are you saying you believe the one nipple breather may be a little small and needs to be opened up some? I recently made the swap from a 2 nipple to the later model one nipple.
jefft

 

[dickymo]

jayel!
Well you were right I took off the breather box and pressed out the two way hose barb, ran down to Home Depot and picked up a 1/2 npt to 3/8 npt reducer then I tapped the breather box with a 1/2" npt tap, and installed the reducer then attached the 3/8" elbow fitting.
I have not as of yet determined the best way to go ie, should I now go with a check valve, and a small filter,, any feedback on this?

 

[5twins]

If you use a check valve then you shouldn't need a filter because oil mist will only be flowing one way - out.

 

[dickymo]

5twins!!
I agree about not needing a filter, but I do live a arid part of the US that has a very arid climate hence allot of dust and at times I do a small amount of riding is on gravel roads, im surrounded by allot of farm land so there is a ton of dust in the air.
That in mind I was thinking a filter would if nothing else would provide piece of mind by keeping that 1% of grit that might possibly get past the check valve..

 

[thelowlife]

Wow seems like these questions have popped up a few times just within the past couple of days.. well here is my solution.

I cut the original 'y' and used a small piece from it to fit properly (I'm sure you can go to home depot or something and get some barbed fittings to work as well so you don't have to cut anything) then attached a reed valve from mikes and voila.

 

[XSLeo]

Jefft, yes, the hole is a bit small. This resriction is a bit much and can lead to early seal leaks and leaks at questionable gaskets.
Lowlife, very nice. I might just add a hose to the outlet of the reed valve so any oil blowby gets carried to below the engine. Any drips from there won't land on top of the transmission and make less of a mess.
Just a thought, the hose can lead into a catch can instead of on the bottom of the bike and the ground.
Leo