Oil Breather Check Valve

[fredheiler@aol.com]

I rebuilt my entire R75/5 engine, and it runs well; however, I can't find the oil breather check valve (#3 below). Am I gonna end up with an oil-soaked air cleaner running without one? Other possible ramifications?

Since the factory check valve is $50+, I'm considering buying a $5-10 generic one and splicing it into the oil breather hose. Would that be a problem?

1725 - ENGINE HOUSING​

 

[20774]

Can't find it?? Not sure what you mean. EuroMotoElectrics has it...this list a price of $33. MaxBMW has it for the mentioned $50+

I can't imagine trying to find something that will do the same thing. I think the BMW part is designed to work with the understood pressures from the engine crankcase. Can a generic unit do the exact same thing? If not, you invite over or under pressure in the case...could affect engine seals.

 

[fredheiler@aol.com]

Can't find it?? Not sure what you mean. EuroMotoElectrics has it...this list a price of $33. MaxBMW has it for the mentioned $50+

I can't imagine trying to find something that will do the same thing. I think the BMW part is designed to work with the understood pressures from the engine crankcase. Can a generic unit do the exact same thing? If not, you invite over or under pressure in the case...could affect engine seals.

Hi Kurt:

Thanks for the prompt reply! Yeah, I'm puzzled about where the valve went; I had all the engine parts organized in a bunch of boxes, and perhaps the valve slid under a flap in the bottom of a box. Anyway, I threw out the boxes (after looking through them carefully) when the project was done, and it's gone.

Just wondering how important (or not) the check valve is; guess I should try to find its opening pressure. I recall most engines didn't use them until well into the 1970s, and I was under the impression venting oil fumes back into the intake was purely a measure to reduce HC emissions.

 

[Omega Man]

You went to all that work. I wouldn’t skimp now. The pressure needs to go somewhere.
OM

 

[20774]

It's more than just venting or trying to removed carbon emissions. With the pistons coming from top dead center to the bottom of the stroke, there's build up of pressure in the case. If the pressure isn't vented properly, it will reduce engine efficiency. Plus with that excess pressure, it will try and find a way out and often that is through the engine seals...leading to new problems.

 

[stevenrankin]

LOL, I first thought you couldn't find the unit on the engine block, forgive me for thinking that. Yeah things can disappear during restorations, the longer the restoration the better chance something will end up lost or misplaced.

I would go to either EME or BMW and spend the money for the part. Frankly these days I know Max BMW deals with EME on occasion so I question the BMW source of parts.
It very well could be the EME part is the exact same as the BMW part, or maybe not. Either way, both will most likely work fine. St.

 

[robsryder]

Snowbum has a discussion about the breather system (it is down the page a bit - look for the heading "Breather System"). It might be worthwhile to see what he says.

BMW Airhead motorcycle Oiling and Breather Systems

BMW motorcycle, Airhead, snowbum, snobum, oiling system, breather disc and reed breather, breather system, oil temperature thermostat

bmwmotorcycletech.info

Somewhere (don't recall where) I read of someone having difficulty with the extraction and replacement of the breather valve. If I recall correctly there was cold (e.g. freezer) used on the new breather valve and heat on the engine case (or at least area about breather valve) to help these tight fitting parts come together more easily. [Anyone else recall the details or source of the troubled install / extraction??] Snowbum does mention the heat / cold for installation as well as a suggested orientation. I find Snowbum's stuff requires careful reading.

 

[20774]

Somewhere (don't recall where) I read of someone having difficulty with the extraction and replacement of the breather valve. If I recall correctly there was cold (e.g. freezer) used on the new breather valve and heat on the engine case (or at least area about breather valve) to help these tight fitting parts come together more easily. [Anyone else recall the details or source??]

It's right there near the bottom of Snowbum's page.

I don't recall have much trouble when I replaced mine on the /7. Other than getting the old one out. I ended up fashioning a slide-hammer to pull it out. Guess I didn't read anything about heading the case around the valve. Going in wasn't much of an issue...it was interference fit but I think it was easy enough to tap it home.

 

[clmedlin]

There’s a video on Boxer2valve’s r90/6 barn find that depicts how to remove it easily with a cotter puller. I followed his technique and was easily able to pull the old style breather assembly out and replace it.