• 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.
• Change the oil in the transmission, drive shaft, and final drive to have a clean starting point.
former Airmarshal, IL.
• James has given you excellent advice and information. There are actually 3 reservoirs of gear oil in an /5 Airhead, and the drive shaft is one of those. The drive shaft U-joints and splines are lubricated by splash within the drive shaft housing. Some of that will end up in the drive shaft boot.
• The oil recommendations in your owner's manual are woefully out of date. In 1976 there was no such thing as synthetic gear oil or multi-viscosity gear oil. These newer oils are far, far superior and prove themselves by improving shifting and lowering the final drive running temp.
I highly recommend the use of Valvoline 75W140 gear oil in all 3 housings. Two quarts will refresh all 3 reservoirs. The oil in these 3 reservoirs should be changed once a year, not due to mileage, but due to water accumulation.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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