ES2 Engine breather

Hi,the NOC shop have the breather you are missing. Only missing the the breatherpipe from the breather to the gearbox sprocket.

Regards from Svein.

The missing ball valve allows air to be expelled from the crankcase during the piston downstroke. On the upstroke the valve closes and prevents air being drawn back into the cases. This lowers pressure in the cases (maybe to the extent of creating a partial vacuum). As crankcase pressure expels oil from whatever weak spots it can find good breathing helps keep the engine oil tight. Unless the engine has wet sumped it does not expel oil from the breather (even without the ball valve), just oil mist.

An alternative to the ball valve is a fuel system non-return valve fitted on the end of the breather pipe. With a larger cross section it should be less restrictive than the ball valve, presenting lower resistance to flow and so reducing crankcase pressure more effectively. The BSP union on the crankcase can be drilled out to match the pipe bore to further reduce resistance to flow.

Ian McD

I have a 1934 Big 4. There is the same breather pipe comming out of the sump just near the drive sprocket, I only have a pipe connected, NO one way valve.  Could  this explain why I have so many oil leaks around the sump.  

does not look like a separate component. It is built into the BSP union, so maybe you do have one fitted to your crankcase.

Another source of excess crankcase pressure is combustion gases leaking past the piston rings. From what you have already said about the size of the ring gaps I think this may be more significant than the breather.

Thanks Ian for the explanation. 

I don’t have a ball in my breather (I took it out) and has a small air filter at the end of the tube under the seat. This was one of the many things I did to stop the bike pooling oil on top of the piston.  I think that was caused by over oiling of the head and is now resolved.

the bike works fine without the ball. I think Mike P removes them from his engines. 

dan 

Richard

On my M 50 I fitted a reed valve from a Yamaha or Beta,(not sure which) all leaks cured ! crankcases now have negative pressure, and the only minor  point after 4k miles is, the cy head bolts rusting, as the engine is so oil tight.

Regards John O

Hi Richard,

   If you have a heavy right hand you can't have too many breathers. This is an open system with 2 crankcase and 1 rocker-box breather pipes, because that ball bearing can't reciprocate fast enough at 6000 rpm and it's not big enough either.

I removed my breather I fitted a "duck bill" from Hitchcocks, which is just a flatted off lenth of rubber that breaths out but not in. It cost next to nothing, is incospicuous,and works. Iv looked on their Web site but can't find it now.

I can't figure out how to post a link, but do a Google search on duck bill nrv and you will get the idea..

E Bay Royal Enfield duckbill breather pipe and clip 140167.

I point it at the rear chain, although there is very little oil comes out of it.