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Topic-icon '76 R90/6: Breather drain port location

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2 weeks 6 days ago - 2 weeks 5 days ago #6809 by 8200
Greetings, all. '76 R90/6, build date 01/75. Uses oil have rebuilt the top end (rings, valves, guides, etc) and it still uses oil. Referencing various posts in Airmail recently, there is supposed to be a drain port from the crankcase breather. I have the breather out again and am unable to find where the port is supposed to be, so I can verify it is clean. Has anybody got a photo or drawing of where I can find said port? All I can find is what appears to be a rough casting in the area. I would really like to be able to ride this bike and not have to carry a lot of oil.

Randy
ABC 8200
Last edit: 2 weeks 5 days ago by Wobbly. Reason: Mods altered title

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2 weeks 5 days ago #6811 by Wobbly
Replied by Wobbly on topic '76 R90/6: Breather drain port location
Welcome Aboard !

The subject breather and collection well lie under 2 thumb-sized covers on the RH side, under the electric starter. You can gain easy access by removing the top engine cover. The breather rubber hoses are generally no longer available, so be very careful when working with the rubber parts.

You could have one of 2 issues...

• The early style breakers used a phenolic disc (similar to circuit board material) that eventually gets chipped and eaten up. The disc needs replacing when it no longer makes a good seal (which was usually about 15 years ago !), but the better repair is to install the later model all-metal flapper valve that never has any issues. The parts fiche will probably guide you to that decision if you look up the replacement parts.

• The well is located under the second breather cover. There's a small depression (or "well") in the top of the engine that collects liquid oil droplets. In the bottom of that cistern is a small hole to allow the oil back into the engine.

If your breather is indeed blowing oil, then your air filter stands a good chance of being oil soaked. So you might check that as well.

Hope this helps.

Don't hide 'em, Ride 'em !!
#15150

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2 weeks 5 days ago #6814 by 8200
Replied by 8200 on topic '76 R90/6: Breather drain port location
Therein is my problem. At the right rear of the block is the vent valve(called non-return valve on the fiche). I have a new hose that goes from the valve cover to the right side airbox clamshell. I don't see anywhere in the well below the valve any holes, just a lot of rough casting residue, as in bumps. If I understand correctly, there is supposed to be a small drainback hole visible that I could use a wire to verify its cleanliness. So far I haven't found the hole. I have sprayed carb cleaner and brake cleaner in the well and it appears to go somewhere faster than just evaporating, so I presume it is finding its way back to the sump. I have tried probing with thin stiff wire at likely indications of pits or maybe holes to no avail. Maybe it doesn't exist on my engine. Or maybe I could drill one of my own?

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2 weeks 5 days ago - 2 weeks 4 days ago #6816 by 15087
Replied by 15087 on topic '76 R90/6: Breather drain port location
I feel your pain, Had the same experience searching for that tiny drain hole, It's there!
Check Snowbum's site under the link below. There's a good photo of said port and a whole oil system schematic.

bmwmotorcycletech.info/oilsketch.htm

favorite airhead I've owned, the one I'm now ridin
Last edit: 2 weeks 4 days ago by Wobbly. Reason: Added missing web link

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2 weeks 2 days ago #6839 by 8200
Replied by 8200 on topic '76 R90/6: Breather drain port location
Thanks for the info. After perusing 'bum's site, it appears that my engine probably doesn't have the drain port in the breather cavity, based on its date of manufacture. So I think I'll have to look for another cause for the usage.

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2 weeks 2 days ago #6840 by 15087
Replied by 15087 on topic '76 R90/6: Breather drain port location
Yes I was thinking that also but you never know exactly when updates and changes were made on these old airheads.
Reference your oil usage I slowed mine down drastically by taking Oak's recommendation and switching to Golden Spectro 20/50 SYN. Believe it can take the heat our engines produce.

favorite airhead I've owned, the one I'm now ridin

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