one way valve for breather? still a good idea?

[KentMoney]

I was reading a lot of discussion regarding putting a one way valve on the breather hose to create negative pressure in the crankcase. However, all the discussion dates back at least a year.

I wanted to know if this was still considered sound thinking or if the general idea has changed on this?


Thanks!

 

[5twins]

As far as I know, most of us are still doin' it, lol.

 

[Tomterrific]

I put a check valve on my Triumph breather a long time ago. I put a check valve on my XS650 breather later. They both seem to be doing fine with the inexpensive vacuum booster check valve. I say it's an A#1 way to minimize oil leaks on a 360° engine with a few miles on the seals.

Tom

 

[oldbiker]

hi all i did on the breather when i removed the air box for pods ,,,,was 2 square bits of fine st/st mesh from the hardware and wrapped them around the new short hose and then tied it up with copper wire ,,,never been a problem ,,,,, regards oldbiker

 

[KentMoney]

would this work?

when I reassemble my bike I am going to run a non-vacuum type petcock. That leaves the old vacuum tube barbs on the intake rubbers mounts free to use. Can I hook up the breathing hose to one of these vacuum barbs? would this accomplish the negative pressure we are all trying to get?

 

[5twins]

I don't think that would do it. I don't think the 1/8" vacuum nipples are big enough.

 

[xjwmx]

I think using your intake barbs in this scenario would just create a lot of havoc.

I think the negative pressure idea might make sense if you had leaks you wanted to stop. Otherwise I think it might be as bad for your sealing as positive pressure, except nothing would come out. Plus when the pistons rise they'd have the resistance of that vacuum being created behind them. Maybe not great for hp.

 

[DirtyErnie]

The low pressure inside the crank case is a fairly common hot-rodder trick and does good things for oil seals, piston ring seal, and reduces power loss due to 'windage' of the moving parts. I can't say I've ever heard someone losing power by doing this, and our parallel twins are the perfect set-up to to do this on the cheap. The rephased engines would make it work, too.

 

[Tomterrific]

You can't use the manifold vacuum for a crankcase extractor. The idle mixture would be forever messed up. The 360° pumping of the pistons is enormous and all you want or need.

Don't use a PCV valve because they check in both directions.

Tom Graham

 

[grizld1]

www.krankvent.com . It costs an arm and a leg, sounds like a marble shakin' in a can, and works every bit as well as claimed. Bonus: you get to play dumb, act real worried, and mess with their heads when smart guys treat you like a rookie and start trying to diagnose the "knock."