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Discussion Starter · #1 ·
My bike decided to go full rich. Took a ride to the mountains for some trout fishing, about 130mi away and approximately at the 100mile mark I needed gas. WHAAAAAT??? I actually had to fill the tank to get it the rest of the way to the stream. Coming back I could watch the fuel gauge moving rapidly to empty. Long story short I'm getting 20mpg. I stopped at Asheville NC Eurosport BMW and they were nice enough to hook up the analyzer and all the sensors are good but they they said the throttle sensor was at 1.84 degrees and should be 0.43-0.65 degrees. Not sure how that could change.
All four plugs were black from running rich, I mean soot black. So I checked the fuel pump, 52psi., installed a new fuel pressure regulator, fuel filter, air filter, O2 sensor and plugs. Compression is 196lbs across the board and all valves are withing spec. Took it out for a ride the other day after all this and it ran like a scalded dog.........for 25 miles then went rich again and the plugs are black again........sigh. I do have an appointment to have the Charlotte BMW dealer look at it at the end of the month. Thoughts?
 

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I'll relate something similar I had with a VW Golf II GTI in Germany. Like your bike, it suddenly ran rich and the coolant gauge was normal, meaning the computer probably thought it was cold and compensated. Took to the VW dealer (much better experience there) and they quickly found the ground to the coolant sensor was bad. I assumed the signal to the gauge would be seen by the computer but apparently they're two different inputs.
 

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Discussion Starter · #3 ·
I'll relate something similar I had with a VW Golf II GTI in Germany. Like your bike, it suddenly ran rich and the coolant gauge was normal, meaning the computer probably thought it was cold and compensated. Took to the VW dealer (much better experience there) and they quickly found the ground to the coolant sensor was bad. I assumed the signal to the gauge would be seen by the computer but apparently they're two different inputs.
Interesting, so you temp gauge was reading normal? If so I wonder how the gauge read normal with a bad ground.
 

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Discussion Starter · #5 ·
Well this is interesting. I performed another fuel pressure/leakdown test and everything is normal. 53# pressure and 1/8# leak down at 2min mark. So after everything I did over the last two weeks the last thing was the fuel additive Mr. Gasket Cataclean. I did however eliminate the crankcase breather to the back of the throttle bodies and ran a separate hose from the crank to the back of the bike to vent to the ground.....EPA be damned. I poured in 4.5oz of Cataclean into a half full fuel tank and rode it 25mi on the highway then stopped and filled it full and rode 25mi back home. The trouble seems to have disappeared! The next day I filled the tank again and rode it 70mi all highway, filled it and am back to my regular 43MPG with lot's of ponies...no issues. So now I went after my oil leaks and found my buddy that was helping me with the original input shaft bearing/seal replacement seems to have forgot to use gasket sealer on the cover plate to the transmission.....something I was suspicious of from the git-go but how do you accuse your good friend of effing up. It saturated another clutch disc and I decided to replace yet another rear main seal (output shaft seal) and o'ring again and I should be fine. The excessive oil in the throttle bodies/airbox have gone since I redirected the crank vapors. I still may have valve seal or ring blowby for the cranks to push so much oil out but at least it's not fouling my fuelsystem with oil now. This will give me time to look for an older K1200GT with low miles and use my bike for parts and ride til I can't ride anymore.
 

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While I'm usually suspicious when a problem cures itself, I'm also a sucker for a story with a happy ending. The temp senor seemed like the most likely culprit, but those things usually don't go out and come back on their own, save for the intermittent short or something. Maybe there's a pressure regulator somewhere that didn't register the thinner air at the higher elevations? Maybe a weak O2 sensor? Also, in your buddy's defense, maybe he was thinking wet clutch?
 

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Discussion Starter · #7 ·
While I'm usually suspicious when a problem cures itself, I'm also a sucker for a story with a happy ending. The temp senor seemed like the most likely culprit, but those things usually don't go out and come back on their own, save for the intermittent short or something. Maybe there's a pressure regulator somewhere that didn't register the thinner air at the higher elevations? Maybe a weak O2 sensor? Also, in your buddy's defense, maybe he was thinking wet clutch?
I'm suspicious to of things that repair themselves..believe me. The 02 sensor was replaced and the pressure regulator so I;m just wondering if maybe it took a little time for the ECU to make the adjustments with the new parts. Went for a mountain run this past Sunday and it ran flawless. The inside of the exhaust is a lovely light brown tinge and NO oil leak whatsoever. Heading to Ohio from NC this Friday for the weekend and next month back to Ohio for the AMA Vintage Days. So Far So Good.... Oh yeah, new Michelin Pilot-4 tires help a lot too.
 
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