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Topic-icon '76 R75/6: What is This Oil Leak Telling me ?

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2 weeks 6 days ago - 2 weeks 5 days ago #6807 by kemartin3
Oh exalted brain trust of all things airhead,

I have a new oil leak on my 1976 R75/6. I've owned it since new, and have always run the oil about 1/2 qt below full (i.e., halfway between the "1" and "2" marks on the dipstick). Recently, I checked it after being parked for a couple of weeks, and found it to be down to the "1" mark on the dipstick. Shame on me, I know. So I dutifully added 1/2 qt of oil. The next day I went for a short ride (10-15 miles) with a couple of friends. When we stopped, it was dripping a significant amount of oil off of the bottom of the engine. Sigh. A couple of days later I cleaned things up and rolled it back into the garage (never started it). No more drips. Today I sprayed anti-perspirant around to get a good layer of talc. I started it, and ran it for about five minutes at around 2K rpm. And, voila, the leak showed itself. It is coming from a slotted screw head on the LH side of the engine case, directly below the oil pressure sender. I've checked the parts fiche, my old Clymer's manual, and dug around here and on Snowbum's site. I can't find anywhere that hints at what that screw it for. Does anyone know what that screw does, and what a leak there might be telling me? I won't guarantee that I didn't overfill it, but after 40+ years, I'm reasonably sure I've got that process down.

Thanks,
Kevin
Last edit: 2 weeks 5 days ago by Wobbly. Reason: Mods altered title

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2 weeks 6 days ago #6808 by 8166
Replied by 8166 on topic What is This Oil Leak Telling me.
Pretty sure what you're looking at is a plug in an oil galley, Kevin. They've been known to leak after all these years. Pretty easy to fix, with one catch. Somehow you need to get both the plug and the hole squeaky clean, which means you'll need to keep the oil inside the engine while you preform the repair. Easiest way to do that is to the lay the bike down onto the right side cylinder head. Put down some plywood or cardboard to protect the valve cover first. And maybe break the plug loose before as well. Then use cotton swabs and pipe cleaners, along with a good solvent like acetone or 100% isopropyl alcohol, to get all the threads spotless. You'll also need a sealant on the threads, something like ThreeBond 1209 or LocTite 518 would work well. That should last for the rest of the bike's life, if not yours.

Congratulations on keeping your /5 on the road for so long, and best wishes for many more miles to come!

8166 Scot Marburger, This email address is being protected from spambots. You need JavaScript enabled to view it.

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2 weeks 5 days ago - 2 weeks 5 days ago #6812 by Wobbly
Your best sealant for that plug is going to be LocTite 518 (aka Permatex 51813) Gasket Maker. Neither set of threads will need to be surgically clean to make a lifetime seal, but it won't hurt either. Take all the time you need, because the sealer only 'cures' in the absence of air. The plug will go back on just as you expect, and you'll be able to easily wipe all traces of excess sealer off the outside of the engine. And the sealant will not only stop the leak, it will also have a slight plug retention effect. So you won't need to go through extraordinary effort to keep it in place.

Hope this helps.

Don't hide 'em, Ride 'em !!
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Last edit: 2 weeks 5 days ago by Wobbly.

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2 weeks 5 days ago #6817 by kemartin3
Replied by kemartin3 on topic '76 R75/6: What is This Oil Leak Telling me ?
Thanks all for the information. Looks like I have a "workshop moment" opportunity awaiting.

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