need help with engine breather hose on 1971 R75/5

Hi everyone, and thanks again for your help and guidance.
below is a picture of the breather hose that BMW sold me.

I realize its the wrong one... must be for a later year of breather system
the bike came to me with nothing...
so I don't know what the stock set up should look like


does anyone have advice... or a picture of what It should look like for an early /5 like this?

thank you in advance.

brant
1971 R75/5

Should look pretty much like #9 in this picture:

https://www.realoem.com/bmw/enUS/showparts?id=0260-EUR-01-1971-2476-BMW-R75_5&diagId=11_1734

On Max's site they show the hose you have but have this statement:

"The original (straight) hose has been discontinued by BMW. The new improved hose has an extra curve (see photo) that requires a new gasket, breather (straight up outlet), and gasket ring. You may not need a new breather if you already have the improved version."

Seems like they expect you to have a new cover which appears to have a top outlet as #5 in this picture:

https://www.realoem.com/bmw/enUS/showparts?id=0363-USA-02-1979-248-BMW-R65&diagId=11_1712

You might try people like Tom Cutter or Ted Porter to see if they have any suggestions.

thank you Kurt.

that picture of the newer style cover makes sense... I didn't realize its output was upward...

in my photo of the cover.
there is a hole in the vent passage... (where the hose should enter the cover)
its not threaded...
but something must go in there to close the potential leak....

has anyone got any advice about what should go into that cover hole?

This is the part you need:
https://www.euromotoelectrics.com/product-p/venthose146.htm

And this is how your breather hose should be routed: attached to the breather with a hose clamp, routed through the small hole in the right airbox half, down into the right carburet intake.

thank you Gary,

that makes sense... I'll get the correct hose...

I suppose the hose will block that small passage as it passes through the right side air filter cover.

anyone know why the factory created that hole... in the pass through?
anything I'm supposed to put into that hole?
maybe its a machine passage.. but doesn't seem necessary..

brant

As Gary has drawn, it goes through the hole in the side cover. As far as I know, nothing goes in that other hole. Here's the breather hose installed in my /7.

Kurt,

perfect picture
and thanks for the answer


as I look at your bike
It prompts one more question....

Regarding your Right upper nut that connects the engine case (stud) to the transmission housing...
In your picture..... (just above the fuel line cross over space)


On my hardware (new kit)... the stainless nut they gave me to make that Engine-trans attachment
its too large of an OD diameter to fit into the slot on the Right air-filter cover.

is that supposed to be a smaller special nut?
or is there a spacer that allows the cover to slide on after the nut is already tight?
I see your nut is removed in the picture... so maybe it pinches the airfilter cover and is installed as the cover is installed?




sorry for doubling up on questions
but your picture is perfect
brant

This picture shows something that is supposed to be attached right there:

https://www.realoem.com/bmw/enUS/showparts?id=0333-USA-09-1977-2474-BMW-R_100_7T&diagId=13_0480

Called a clamping spring. I don't remember exactly, but I think the right side cover slides into place under this clamping spring and also on the other one on top of the transmission. When the left side cover is put in place and the long bolt goes through the air filter, it holds the two covers in place. I might be missing a step in there, but that seems like how it's supposed to work. Look on the left side...similar set up there.

Yes, there is a special flanged nut with 12mm flats that is used there. Much easier to get a wrench onto.

The hole that Kurt pointed out near the dipstick is a drain for the starter compartment on top of the engine. The nut you’re referring to is a standard nut. Nothing special. I usually have it threaded most of the way and then slip the airbox cover behind it. First insert the breather hose through the cover, then pivot the airbox cover so that it slips behind the washer and nut, and under the clip on the top of the transmission, slide the airbox into position and tighten the nut holding the airbox and transmission in place.

One additional note: if you’ve just installed your transmission, make sure that it’s aligned properly. To do this, before tightening the trans bolts, I hook up the clutch cable and the battery. I use the electric starter to turn the engine while working the clutch lever in and out. Then while holding my thumb on the seam of the engine and trans to sense any movement. There shouldn’t be any. If there is, work the clutch some more while turning the engine. No more movement means it’s aligned and ready to tighten. If it’s not aligned you can end up with premature spline wear on your clutch components. Goo luck and have fun with your project. It’s great therapy!

20774 said:

This picture shows something that is supposed to be attached right there:

https://www.realoem.com/bmw/enUS/showparts?id=0333-USA-09-1977-2474-BMW-R_100_7T&diagId=13_0480

Called a clamping spring. I don't remember exactly, but I think the right side cover slides into place under this clamping spring and also on the other one on top of the transmission. When the left side cover is put in place and the long bolt goes through the air filter, it holds the two covers in place. I might be missing a step in there, but that seems like how it's supposed to work. Look on the left side...similar set up there.

Click to expand...

oops...
sorry I was not descript enough
I have the spring and spacer for the drivers Left cover

but I was referring to the drivers right cover in your picture... and the nut that tightens on the engine stud that sticks through the trans

sounds like it is supposed to pinch the cover as you tighten the nut. not slide over, like I assumed...

thank you everyone.
and really good advice on checking my trans/clutch alignment right now.. before I proceed.

I found the correct vent hose at EuroMotoElectrics.

https://www.euromotoelectrics.com/product-p/venthose146.htm

I'm back with yet another question
sorry I have not laid this one to rest yet.

So I got the NLA vent hose sold at EME/Max
also the sealing ring in the first diagram, that Kurt posted

thought I would finally put the covers on today
but the hose is too large of an OD to fit into the cover passage hole

only if I roll/crease it in half will it go through
not like the picture of your /7 Kurt
and the sealing ring doesn't have an apparent purpose?

my cover hole OD looks about the same size as your picture of the /7 also... (judging from the screen shot by eyeball)

sorry if I'm making this too difficult
I can't imagine that the hose it wrong? but still has the correct curve

weird.



I hope everyone is going to have a happy thanksgiving!
brant

That is an airbox half for the dual breather system, 17mm hole.

http://largiader.com/articles/intake/

Manufactured in February of ‘78. Not the original from a ‘71 R75/5.

I'm sure BMW gave up on trying to describe the different breather system parts that were used in the '70s, but broadly the clamshell airbox systems shake out into 22mm single hose and 17mm dual hose. The P-shaped hose with the wax ring is a hybrid, where they're using a 17mm single hose in a system designed for 22mm single hose. The wax ring is only for that specific use: using a 17mm hose in a 22mm hole. And I think it is a recent thing that was added to the fiche; ten years ago when I was buying the P-shaped hose to replace the NLA straight hose I cut a section of the old hose and jammed the new one through it to fill the gap. I don't remember the wax ring being suggested at that time.

I'm not sure if that P-shaped hose was ever used in production. The non-R65 engine housings changed to have the large breather chamber, and there was briefly a single hose for that system and then the square airbox came along with an entirely new setup. AFAIK the R65 first got dual hoses and then got a unique hose feeding the square airbox.

I had a '78 in the shop with the dual 17mm holes and it needed a breather system. I probably should have bought the '77-only 11 15 1 265 039 hose and changed the right airbox cover to one with a 22mm hole, but I ended up fabricating a system using some later parts. It is a PITA that this is described so poorly in the fiche and that so many parts are NLA.

Thank You!

I was wondering why there was a slot for the O'ring on the output sleeve on one side..
and no channel for the other side... just the smooth output.

crud.. ok... so one side of mine is non original
I guess I'll look for a replacement side.

thank you!
brant

Or buy a vertical breather and use the P hose, which should fit nicely and will do a better job. But it's probably a lot more expensive that way.

You might find a machine shop that can bore that 17mm opening out to 22 mm. From the photo it looks like there is room to do that.