'93 K100 LT Fuel leak

Hello,

I have a '93 K100 LT, yesterday after riding home from work and parking the bike, I noticed several small puddles & one large puddle. It was fuel, dripping from the tank vent. The tank was not full, I had ridding about a 100 miles after a fill up. There appears to be some type of chamber at the top of the tank that the vent line taps into. I suppose the chamber is supposed to separate liquid from fumes. Any ideas why this would happen?


Regards,


Richard Flood
Commerce, MI

Richard,

When you say that the fuel is leaking from the tank vent, do you mean that it is coming from the hose down by the right peg plate? Most US bikes originally came with the tank vented to the crankcase, so if fuel is coming out of the hose by the peg plate there are several possibilities.

The first thing that I would check is the seal around the filler cap. If that is allowing fuel to slosh into the well around the cap fuel would exit throughe the rain drain and out through the peg plate hose. This would happen with both the US and European venting systems. The rain drain is the hole that is at 9 o'clock on the fuel cap base.

Hello, Thanks for the reply. Yes, the fuel is dripping from the tube down by the right foot peg. The tube is connected directly to the vent on the tank.

Regards,


Richard,

Commerce, MI

1993 K 100 LT

Possibly an overfill? Or filled full and let sit in the sun? Happened to me several times with my 100RS after I rerouted the line so it no longer dumped into the engine....

Richard,

Do you still have the flapper in the filler hole under the gas cap? If not, it was probably overfilled. Have you been able to repeat the problem?

Hello all,

Thanks for the reply's.

58058D, I had ridden about a 100 miles on the tank, so there was probably 2 -2 1/2 gallons still in the tank.

98 Lee, the flapper has been removed and the problem hasn't happened again. I've had the bike since July and this was the only time I noticed the fuel dripping from the vent.

Do you know the purpose of the chamber/accumulator on the inside at the top of the tank? That is where the vent tube connects on the inside of tank.

If by chamber you mean a black plastic bubble sort of thing, it has a small hole in the top but (I think) is simply intended to prevent fuel splashing into the vent tube.

Hello PGlaves,

The chamber/accumulator in my tank is made of aluminum. I think you are correct the accumulator is there to separate the liquid from vapor and is there to prevent liquid fuel from entering the vent tube. There is a small diameter hole in the bottom that would allow liquid to drip back into the tank and as you indicate, a hole in the top. If the hole in the bottom became blocked I guess that would allow liquid to eventually make it's way out the vent tube.


Regards,

Richard Flood
Commerce, MI

The flapper serves two purposes. It prevents the old larger diameter leaded fuel nozzles from being used and it limits the level of fuel in the tank to below the vent tube assembly in the top of the tank.

If you remove the flapper and fill to the neck, the fuel will run out the vent tube under acceleration and cornering. To prevent pouring gas onto the ground, stop filling about 3/8" from the neck (still more fuel than if the flapper was still in there.)