K11 Owners Group

N41EF · Posted: Sat Aug 01, 2015 2:00 pm Post subject: Vapor Lock or Heat Soak?

So, dark bike, sits in the 95 degree sun, and pressure builds up in the gas tank enough that the bike doesn't want to start. Did it a couple of times last year, and twice this week. It's like pressure builds up in the tank, and the engine will spin over but not start. If I open the gas filler I hear a large swoosh, then the bike will start.

If he bike sits a few minutes it isn't a problem. It sat for about 30 minutes in full sun this afternoon and did it.

The fuel pump sounds normal, I've replaced the fuel filter, I'm stumped.

Any one had a problem like this?
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2014 R1200RT Water Cooled
2001 R1100S Light
1993 K1100LT. Nissan Ice Blue.(Gone)

rbm · Posted: Sat Aug 01, 2015 3:16 pm Post subject:

One of the two pipes exiting the bottom of the tank on the right rear is an internal vent. So, if this is plugged, pressure may build up as you observe. Have you checked that this tube is clear.

The tube of interest begins just under the gas filler cap:

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- Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer

N41EF · Posted: Sat Aug 01, 2015 4:28 pm Post subject:

I wasn't sure if he tank was vented, or not. I'll check, thanks!
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2014 R1200RT Water Cooled
2001 R1100S Light
1993 K1100LT. Nissan Ice Blue.(Gone)

Flying Duck · Posted: Sat Aug 01, 2015 5:09 pm Post subject:

It is also possible that the line from the rear vent pipe got kinked the last time the tank was re-installed. (It is supposed to drain under the right peg plate.)
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93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
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John Clauss · Posted: Sun Aug 02, 2015 8:12 pm Post subject:

Many years ago I took the experienced riders course and I topped off right before I got there. The engine heat had gas dripping out of the vent pipe pretty quickly. I let it sit a little and I was all good. It is important that it is functioning properly.
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1997 K1100LT
1975 R75/6

It will bring you so close to nausea, it will make you sick! - Big Al

BobZ(IL) · Posted: Mon Aug 03, 2015 8:51 pm Post subject:

During my recent western states trip, I opened the filler lid too quickly at a gas stop and had a 3 foot column of fuel shoot up and all over the bike and me. Pretty scary but no harm done. Never had a problem with the bike starting or running in the extreme heat.
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'93 K1100LT
'78 R100S
'05 R1200GS
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