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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Kenan on May 10, 2015, 09:10:20 PM

Title: 1996 K1100RS Fuel Tank Overflows Fuel
Post by: Kenan on May 10, 2015, 09:10:20 PM

Hello All,
I am new to this forum. I have a 1996 K1100RS with 76,000 miles on the clock. I have owned the bike since 2005. I have put the last 50,000 miles on the bike.
I have an ongoing problem. When the bike gets hot on any day when the air temperature is above 80 deg F, fuel will run in a steady stream out of the vent tube.
Notes: The "flapper" unit has been removed. The tube into the crankcase has been plugged. The tube that is supposed to go to the crankcase has been routed to drain straight down - the vent tube that now leaks fuel. When this happens, there is pressure inside the tank - If I open the gas filler cap, air escapes and the fuel no longer runs out of the vent tube. I have checked the vent in the filler cap and it appears to be OK - no broken spring.
Any ideas or suggestions will be greatly appreciated.

Best regards,
Kenan

Title: Re: 1996 K1100RS Fuel Tank Overflows Fuel
Post by: The Mighty Gryphon on May 10, 2015, 09:34:52 PM

Does this happen any time the temperature is above 80 regardless of the fuel level, or only when the tank is completely or nearly full?

Title: Re: 1996 K1100RS Fuel Tank Overflows Fuel
Post by: Kenan on May 10, 2015, 09:56:10 PM

It is worse when the tank is full or nearly full but if the air temp is 90 + deg, it can leak gas when the tank is 1/2 full or less.

Title: Re: 1996 K1100RS Fuel Tank Overflows Fuel
Post by: Sebsi on May 19, 2015, 03:54:02 PM

Hi,

You got the same thing I had, which is pretty well documented (with a fix) here:

http://www.motobrick.com/index.php/topic,4658.msg29106.html#msg29106

Basically, your return fuel line (from the FI) is squirting directly into the vent. Heat and fullness are factors. My guess is that a few bikes have tank return lines  which are a few mm's off spec and this weird fluke ensues. Take the cap off and look inside, then turn the key on. See (and hear) that squirt of fuel? When conditions are right (fuel volume + heat) that squirt ends up under your right foot peg. The fix is a challenge for sure: you need to access the return line nipple with a submersible hose and run it down to the bottom of the tank. Easier said than done. PM me for deets. - Sebsi

Title: Re: 1996 K1100RS Fuel Tank Overflows Fuel
Post by: Kenan on May 20, 2015, 08:29:16 AM

Hello,
Note that another member informed me about this modification. I have installed the tubing and the clamp onto the fuel injection return. The air temperature has not been hot enough to fully test since I performed the modification.
Thanks to everyone on this forum for your input. I believe this will resolve the problem.
Best regards,
Kenan