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Author Topic: What Is Causing This Oil Leak  (Read 3984 times)

Offline k

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What Is Causing This Oil Leak
« on: August 23, 2020, 09:06:26 PM »
When I am running for sustained periods above 70, or so, I get an oil leak from the right side of the bike. When I back off, the leak subsides, a bit. The crankcase gasket has been replaced, and the problem is unchanged.
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  • Indiana
  • 1985 K100

Offline blackie1

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  • christchurch nz
Re: What Is Causing This Oil Leak
« Reply #1 on: August 24, 2020, 04:48:37 AM »
can we assume , whilst on the center stand, your engine oil level at rest sits at/near the dot in the center of your sight glass?
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  • christchurch, new zealand , where else would u want to live, really
  • 1991 K75RT naked 67,000kms

Offline stokester

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Re: What Is Causing This Oil Leak
« Reply #2 on: August 24, 2020, 09:19:51 AM »
Quote from: blackie1 on August 24, 2020, 04:48:37 AM
can we assume , whilst on the center stand, your engine oil level at rest sits at/near the dot in the center of your sight glass?
and your oil cap has an o-ring?
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  • Yorktown Virginia
  • '94 K75S Dakar Yellow - '93 K75S Seiden Blau - '91 R100RT Bermuda Blue- '78 R100S Smoke Red
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Offline Chaos

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  • Mars needs women!
Re: What Is Causing This Oil Leak
« Reply #3 on: August 24, 2020, 09:37:30 AM »
I think there's a screw hole in that bottom corner of the airbox, if you're getting enough blowby to collect oil in the filter housing it could be leaking out there.  And check the o ring on the oil filler cap. 
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  • sw ohio
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
sold 6/23
2023 Ural 2WD sidecar (BMW's bastard step child)

Offline Laitch

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Re: What Is Causing This Oil Leak
« Reply #4 on: August 24, 2020, 10:59:53 AM »
If it's pooling at the red arrow, it must be flowing from some place to get there. Clean off all traces of oil then apply bath powder on the area around the upper crankcase cover seam and the pooling area. Blow off the excess, go for a ride at 70mph, stop, then see if any powder residue reveals tracks from the source. It's likely the crankcase seam is leaking, especially if the cover has been off or it has received a shock from the bike's falling over on that side.
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline k

  • ^ Motobrick Curious
  • Posts: 84
Re: What Is Causing This Oil Leak
« Reply #5 on: August 24, 2020, 10:14:21 PM »
I put the oil cap from the K1100 on the K100, put some corn starch on it, and took it out for a half hour.

I can't find a leak.
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  • Indiana
  • 1985 K100

Offline Laitch

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Re: What Is Causing This Oil Leak
« Reply #6 on: August 25, 2020, 01:26:07 AM »
Congratulations on finding the source of the problem.  112350
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline k

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Re: What Is Causing This Oil Leak
« Reply #7 on: August 25, 2020, 06:11:00 PM »
Quote from: Laitch on August 25, 2020, 01:26:07 AM
Congratulations on finding the source of the problem.  112350

I wouldn't go that far. I just didn't spot a leak in a half-hour ride.
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  • Indiana
  • 1985 K100

Offline Laitch

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Re: What Is Causing This Oil Leak
« Reply #8 on: August 25, 2020, 08:23:47 PM »
True, it seems like you didn't go that far. I rescind congratulations and substitute, Have a nice day, whenever that might start.
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline k

  • ^ Motobrick Curious
  • Posts: 84
Re: What Is Causing This Oil Leak
« Reply #9 on: August 26, 2020, 10:31:58 PM »
Still leaking. I can't make it leak with high RPM and low speed. It will leak at high RPM and high speed.
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  • Indiana
  • 1985 K100

Offline Laitch

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Re: What Is Causing This Oil Leak
« Reply #10 on: August 27, 2020, 12:15:03 AM »
Did you try tracing the leak with the cornstarch method again?
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline koapono

  • ^ Proficient Motobricker
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Re: What Is Causing This Oil Leak
« Reply #11 on: August 27, 2020, 06:59:48 AM »
just a thought:
there are a couple of crankcase vents in the area under the air-box. If those hoses/rubber caps are original they might be source of leak. The engine block has many nooks and crannies under the air-box, they may be filling with oil and leaking out in area you highlighted.
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  • prince george, VA (25 miles south of richmond)
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Offline Snowman

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  • Aberdeen SD.
Re: What Is Causing This Oil Leak
« Reply #12 on: October 15, 2020, 05:33:39 PM »
I agree with Koapono, Likely a vent hose either split or out of place. Sustained high engine RPM makes it worse.
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