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Discussion Starter · #1 ·
My 2002 K1200RS presently has 111,000mi. At 70.000 I had to replace the rear main seal, which my buddy and I did successfully. Last fall the transmission input shaft bearing went out so we replaced the bearing and the seal, again no issues until three weeks ago when my clutch started slipping and I noticed oil leaking from the seal where the transmission and bell housing join. We took it apart to change the disc but could not figure which seal was leaking, the new trans shaft seal or the rear main, so we replaced both while we were in there. A few days ago that seam started leaking again, but getting worse, so instead of frying a new clutch disc we tore it apart yesterday to find oil pouring out of the engine at the NEW main seal....WTH?? Back up a little I put UV-oil dye in the trans first...no detection from oil leak it was trans. Put the dye in the engine and the oil leak lit up green, definitely engine oil, but from a brand new rear main seal?? I changed the oil and filter and filled it to my regular 1/4" from top of the oil level glass and Oh Boy!! did the oil pour out of it then. When we split it apart yesterday there must have bee 1/2pint of oil in the bell housing, but luckily no clutch disc saturation. So trans seal is good, engine main seal and o-ring is new, and new main seal numbers match old main seal. So what the hell is it? My though is excessive crank case pressure forcing the oil out of the main seal. Maybe bad rings? Clogged distribution hose, which I replaced around 80,000mi? I am getting a lot of oil in the air-box like reversion issue. Today we will check my cylinder compression and maybe do a leakdown test of the top end. Any and all suggestions are greatly appreciated as always.
 

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Some things to check, though hardly an exhaustive list:
  • Crankshaft grooved at sealing area - the seal can wear away the metal of the cream over time
  • Defective or missing curtain spring on seal
  • Seal damaged on installation

I'd be inclined to pull the seal and inspect it, looking to see if the spring is in place and there are no nicks in the lip. Run a finger over the seal area of the crank to check for grooves and nicks.

I swapped a trans on a truck a few years ago, and managed to scratch the crank with the seal puller despite being fairly careful (though obviously not careful enough). Fortunately, for that engine it's easy to get a seal with a sleeve for just such a problem, so it was a non-issue. I don't know if they make that sort of seal and sleeve assembly for the brick engine, so repairing a worn or damaged crank seal area might involve getting something custom machined to press on to the crank to fix the problem. Hopefully it turns out that that isn't the problem!
 

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Discussion Starter · #3 ·
Some things to check, though hardly an exhaustive list:
  • Crankshaft grooved at sealing area - the seal can wear away the metal of the cream over time
  • Defective or missing curtain spring on seal
  • Seal damaged on installation

I'd be inclined to pull the seal and inspect it, looking to see if the spring is in place and there are no nicks in the lip. Run a finger over the seal area of the crank to check for grooves and nicks.

I swapped a trans on a truck a few years ago, and managed to scratch the crank with the seal puller despite being fairly careful (though obviously not careful enough). Fortunately, for that engine it's easy to get a seal with a sleeve for just such a problem, so it was a non-issue. I don't know if they make that sort of seal and sleeve assembly for the brick engine, so repairing a worn or damaged crank seal area might involve getting something custom machined to press on to the crank to fix the problem. Hopefully it turns out that that isn't the problem!
On my way as we speak to my local dealer for a new seal. The seal surface looks god as does the flywheel which it deals, no scratches or excessive wear. The shaft tge flywheel bolts to is an auxiliary shaft located below the actual crankshaft. The manual states to lube the outside of the seal and assemble with the inner surface dry! That’s how we did it and yeah, doesn’t make sense. I’ll ask a tech when we get there….. Thanks
 

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two K1300S bikes, S1000R & Vespa 150 Primavera clown paint job
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Are you changing the 19x4mm oring in the back of the engine, using a Viton oring? This is the big dog in oil leaks.
 

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Discussion Starter · #5 ·
Are you changing the 19x4mm oring in the back of the engine, using a Viton oring? This is the big dog in oil leaks.
Absolutely, Nut, o-ring and main seal on the first go-round. This time I used the o-ring from three weeks ago. My o-ring that had 40,000mi on it had a definitive flat spot on it. The one from two weeks ago is fine.
 

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Discussion Starter · #6 ·
So my parts guy at Charlotte BMW said in the past they did have some fails with new mail seals and had to re-do customers bikes. I got a new seal from him at half-off. Returned home and installed the seal and finished the job that afternoon and No Leak!!! crossed-fingers. I put several hundred miles on it since Saturday and no leaking. I also am running my oil lever just a tick below the center dot too. So as of now all is well and the new main seal was the culprit........whodathunk? If it still leaked after this second attempt in as many weeks it was going to be pieced out, the Black Mule has been saved.
 
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