another crankcase breather question

[Inked Monkey]

I know it has been covered before, but I can't find a definetive answer. I have a bobber with an 80 motor. I just put a little rubber hose off the breather nipple and installed a little filter. I've heard people say that I need to use a valve of some sort? I have about 3000 miles on it so far, but would a valve help the motor?

Thanks

 

[pa23driver]

a filter on its own is fine... atleast thats how the japanese engineers felt anyway. the original setup was a the breather connected directly to the airbox, with no valve anywhere. but some people believe that having a sort of outlet-only type valve can improve performance by creating a slight vacuum and maybe improve gasket life. up to you, but i'm skipping all the BS and just using a filter.

 

[sreimer]

Venting the breather to the airbox like the OEMs do is what creates the vacuum in a stock motor

 

[XSLeo]

On the original bikes the breather had two outlets with a long hose going down, behind the engine. They found this blew to much oil out. Later they plugged one outlet and used just one hose. Even later the changed to a single outlet breather that was hooked into the air boxes.
On a bike with out the stock air boxes a short hose and the power brake check valve pointed at one of the pod air filters keeps any oil blowby going into the air filter instead of all over the bike.
A short hose and a filter , after the filter gets too wet with oil lets oil flow all over the bike.
I use a short hose, a brake valve and a long hose to behind and below the engine.
The check valve does create a slight vaccum in the engine cases. This vaccum helps seals and gaskets from leaking.
It also helps the rings seal better. This better seal gives more power and less blowby at the rings, this keeps the oil cleaner and less pressure for the check valve to eliminate.
All good things.
Leo

 

[Tomterrific]

Any vacuum in the airbox isn't measureable and is insignificant for our purpose.

 

[retiredgentleman]

Quite right Tom, the airbox is just a convenient place to direct oil vapours that can be burned rather than go into the air.

 

[Inked Monkey]

I've got some weepage on one of my jugs and I'm tired of oil mist on my carbs, so I'm gonna try the valve.

 

[Inked Monkey]

I just went to the parts store to find a brake booster valve. Found one in the help section, but it allowed air to go both ways? I thought they were only supposed to let air pass one way?

 

[TeeCat]

I know the "Help" branded ones are one-way. Failing that, I'm using a Mike's reed valve. They're larger and more expensive, but they are definitely exhale-only.

Make certain that what you found is not a PCV valve. That won't work.

TC

 

[5twins]

This is the one you want, about $5 .....

 

[Inked Monkey]

Thats the one I picked up. Maybe i needed to suck instead of blow in both sides.

Alright perverts! not like that!

 

[DogBunny]

You might have to suck and blow really hard to get it to work. I find a lot of variability in them. I also think they are prone to failing, but they are only $5, and the auto parts store guarantees them for a year. If I had the money, I would buy a Crankvent, I think they work better.