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My Airhead Needs Help
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I am slowly working my way through a 1976 R75 /6 "barn find". It is time to do the spline lube and see if the rear main seal is leaking. I took the clamps off the swing arm boot to get at the drive shaft bolts, and pulled back the top of the boot for a look and went to bed. This morning there was a good 1-2 oz of orange milky oil under the bike. I clean it up before taking a picture. I could still see some when I pulled the boot back (see photo).
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1) Seems like quite a bit oil for something that should have none. I guess the output seal might be leaking?
2) It is orange because water got into the boot? The boot is still fairly pliable, so no major crack are apparent.
Any ideas what might have caused it and what to look for as I continue with removing the transmission?
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Background: The previous owner bought it at auction and probably did not do anything but replace the transmission fluid.
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Posted : 07/04/2026 13:40
The swing arm should have 150 cc's of oil. Some of it will pool in the drive shaft boot. Milky contamination in gear oil is water. I would guess that the orangish tint is rust.
former Airmarshal, IL.
Posted : 07/05/2026 07:10
Change the oil in the transmission, drive shaft, and final drive to have a clean starting point.
former Airmarshal, IL.
Posted : 07/05/2026 07:25
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