Fuel Tank Vacuum - K-Bikes.com - Excellence in Motion
 
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post #1 of 7 (permalink) Old Sep 7th, 2016, 6:53 am Thread Starter
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Fuel Tank Vacuum

Hey Guys, Just did a major service on my 2002 K1200RS, including new fuel filter. When I got to the second servo (after filling a tank and riding 350kms till almost empty) I noticed that the flip-lid for the fuel tank was VERY hard to lift open and once I got it just open i noticed that it was due to a vacuum inside, obviously the tank isn't breathing anymore.. where do i start to check/fix this ? clearly I have all the flow lines correct otherwise I wouldn't have gone anywhere, I thought I had connected the breather lines correctly, but it seems not. Do I need to pull the tank off and pull it apart again and double check all this ?

Cheers.

2002 K1200RS -- more than 100,000Kms on the clock, just ran in.
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post #2 of 7 (permalink) Old Oct 12th, 2016, 12:23 am Thread Starter
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Found the problem. it seems that when i was putting everything back together in the tank that I switch where the overfill and the breather hoses connect to the pipes that transition from in the tank to out of the tank. it turns out that the overflow one was blocked up in that short steel section, and i had connected the breather line to it. not that it should have made a difference which one was connected to which as they just continue on as plain hose and vent to atmosphere. so clearly the over flow hose hasn't been functional for a long time and accidentally switch these around has brought an existing issue to light. i tried to unblock the blockage but no matter what i tried i could not unblock the blockage, leaves me wonder if it has been blocked from the factory when the steel lines were welded in place, as it seems VERY hard what ever is cause the blockage. so for now the over flow has been connected to the blocked line and the vent hose is back to the open one and is thus able to vent. (as it has been for go knows how long). it's a shame cause to really fix the problem would mean replace the entire metal piece that supports the fuel pump etc, which i would assume would cost a lot of money. but at least i now know what the issue is and can work around it.

2002 K1200RS -- more than 100,000Kms on the clock, just ran in.
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post #3 of 7 (permalink) Old Oct 28th, 2016, 5:53 am
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Interesting! I have a K75C (1985) which I renovated - it ran like a dream all summer. Recently the bike fell over! - no apparent damage. Soon after at the end of a 50km run the bike cut out as though out of petrol. The bike would not restart but next morning it started with no problem
I have checked the hall sensor - wiring and I can't find a problem. I was about to ask the question "Can the fuel tank on a K bike air lock? From what you're saying it looks as though they can. Any other comments would be welcome.
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post #4 of 7 (permalink) Old Oct 31st, 2016, 12:33 pm
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Mine did

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Originally Posted by Tegid View Post
Interesting! I have a K75C (1985) which I renovated - it ran like a dream all summer. Recently the bike fell over! - no apparent damage. Soon after at the end of a 50km run the bike cut out as though out of petrol. The bike would not restart but next morning it started with no problem
I have checked the hall sensor - wiring and I can't find a problem. I was about to ask the question "Can the fuel tank on a K bike air lock? From what you're saying it looks as though they can. Any other comments would be welcome.
MY 1998 K1200rs had a fuel lock/vacuum problem, I sorted it out by squirting WD40 and using garden strimmer line to clear the breather pipe. This was situated on the inside of the fuel tank in the filler aperture.
The bike appeared to have ran out of fuel, had I undone the fuel cap it would have made a whooshing noise and would have then probably started once the vacuum was released/broken.


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post #5 of 7 (permalink) Old Nov 20th, 2016, 4:33 am Thread Starter
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Quote:
Originally Posted by Tegid View Post
Interesting! I have a K75C (1985) which I renovated - it ran like a dream all summer. Recently the bike fell over! - no apparent damage. Soon after at the end of a 50km run the bike cut out as though out of petrol. The bike would not restart but next morning it started with no problem
I have checked the hall sensor - wiring and I can't find a problem. I was about to ask the question "Can the fuel tank on a K bike air lock? From what you're saying it looks as though they can. Any other comments would be welcome.
i'd say your bike ran a Carby, and thus when the vacuum in the tank gradually became greater than the vacuum created by the downwards motion of the piston. it would have been running leaner and leaner until it was too lean to fire, and thus stopped. Given mine is EFI, the pump likely didn't even notice as it was still submerged in liquid.

2002 K1200RS -- more than 100,000Kms on the clock, just ran in.
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post #6 of 7 (permalink) Old Nov 20th, 2016, 4:35 am Thread Starter
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Quote:
Originally Posted by zxmark9r View Post
MY 1998 K1200rs had a fuel lock/vacuum problem, I sorted it out by squirting WD40 and using garden strimmer line to clear the breather pipe. This was situated on the inside of the fuel tank in the filler aperture.
The bike appeared to have ran out of fuel, had I undone the fuel cap it would have made a whooshing noise and would have then probably started once the vacuum was released/broken.


Mark
wouldn't this have been the overfill/flow drain ?

2002 K1200RS -- more than 100,000Kms on the clock, just ran in.
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post #7 of 7 (permalink) Old Nov 26th, 2016, 4:24 am
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Originally Posted by Josh_B View Post
wouldn't this have been the overfill/flow drain ?
I think that the 4 rectangular holes are the overflows, and that the single round 2/3mm hole is the vacuum. The one I cleaned out was the small round one, this pipe is one of the two black rubber pipes that come out from under the bike on the right. This was not easy, and in fact I also used a bicycle inner brake cable with the knob at the end cut off and a bicycle pump on both ends of the pipe.


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