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Took bike out over Easter weekend short ride. Had gear oil coming out of bevel. What would cause this?

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
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Welcome! What weight of gear

Welcome! What weight of gear oil are you using? By any chance did you overfill it last time?

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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Final drive

Bevel exhaust

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80/90 hypoid. Worried that

80/90 hypoid. Worried that the swing bar seal might be failing

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I didn't fill last time took

I didn't fill last time took to dealership for maintenance. Never seen it before. Has been sitting in garage over winter. I haven't rode any serious amount of time. Just around the neighborhood to make sure all is well.

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Thank you for the welcome!

Thank you for the welcome! Any advice I greatly appreciate. I think I will drain & measure 250 cc in final drive & 150 cc in swing arm. Should I do both at the same time or do the final drive first or the swing arm first?

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80/90 hypoid. Worried that

80/90 hypoid. Worried that the swing bar seal might be failing

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Let me know your thoughts.

Let me know your thoughts. Thank you

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VBMWMO #7032
San Antonio, TX
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It might be a good idea to

Another question...what was the temperature outside? Somethings if the temperature is low, the oil can foam up and overflow. Also, where was the oil coming out?

It might be a good idea to drain and refill and to start over. If you were to remove the fill hole at the back of the final drive, the proper amount of oil should be just at the bottom of the threads in the hole. If it's much more than that, it could be either the previous service put too much in or oil is transferring from the drive shaft into the final drive.

As for the drive shaft, I would go ahead and drain it as well. The book calls for 150cc in the shaft, but in reality it can be less than than...I typically only fill my /7 with 100cc...less oil means less chance for a pressure situation...and 100cc is more than enough as it gets sloshed back and forth while riding the bike.

See what happens after changing both sets of fluids. Another potential problem although less likely to be the case is fluid is transferring from the transmission into the drive shaft and then into the final drive. Are you sure that the bolt that holds the speedometer and ground cable at the rear of the transmission is free to breathe? This bolt has a hole running down the middle of it. If you're not sure, remove it and poke a small diameter wire through it. When tightening, don't crank down on the bolt...it just needs to be snug.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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The bevel/breath oil coming

The bevel/breath oil coming out

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Tempature was around high

Tempature was around high 40's

schrader7032
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VBMWMO #7032
San Antonio, TX
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40's is a little cool.

40's is a little cool. Possibility that the temps may have contributed. I'd change gear oil so you know what you have, then continue to watch it.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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Okay, will try. I cannot

Okay, will try. I cannot thank you enough for your advice. My uncle left me his bike to before he passed away from cancer. He rode this in Europe & Mexico baja

sminn560sl
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VBMWMO #7977
Central Kentucky
Joined: 04/13/2011
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Vent holes

If you can take the filler plug off of the final drive and the oil doesn't pour out you don't have too much oil in the rear end. In that case I'd check to ensure that the vent holes are not plugged (a pipe cleaner works well).

Photo's from Duane Ausherman:

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Steve in Kentucky
91 BMW K1 (caretaking); 87 BMW R80 (RS); 61 BMW R60/2; 66 BMW R27; 74 R90/6; 59 NSU Maxi; 71 Norton Commando; 71 BSA 250 GP; 66 Triumph TR6R; 61 Norton Manx; 59/61 Triton; 14 Triumph Thruxton

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