K75 Fuel Tank Vents

[cayuse60]

Why were these vent lines disconnected from the fule tank and the one to the crankcase plugged?:confused:

TIA---tim

[98lee]

It is not uncommon to take the vent hose that runs from the tank to the crankcase and disconnect it from the crankcase end and then run it to the right side by the centerstand. The thinking is that any fuel slosh caused by overfilling or any fumes caused by expansion will not find their way into the crankcase thereby compromising the oil. Usually these fumes gas off after the oil has been hot for a period of time. If you do alot of short trips (to the corner store, a close by friends house, etc,) it is thought that instead of gassing off, it builds up.

The two tank hoses (vent and filler overflow can be T'ed together if they go to the area of the right footpe(not left, there is a big chrome hot thing there!) But don't allow the filler overflow to go to the crankcase. If you overfill it , it will put raw gas into your oil.

You said that the hoses "were disconnected from THE FUEL TANK". On later K75 there was a cup underneath the tank vents that would catch anything that came out of the vent tubes and then drain through a hose, but I gather yours does not have this. If you don't have the cup, a hose should be attatched to each of the two tubes and then routed to the right footpeg area.

[PGlaves]

The little plastic funnel that clips to the frame under the tank is called an "air accumulator" and the part # is: 16 13 2 307 467. It positions under the two stub pipes on the tank.

The vent hose running from the tank to the crankcase was disconnected because it was one of those stupid ideas that didn't work out. Fill the tank, and park in the Sun on a warm day, and you were almost guaranteed to dump raw fuel into the crankcase - thus diluting the oil and trashing the bearings. My dealer disconnected this hose and installed the air accumulator (funnel) on my K75 back in '86 at the 600 miles service, 3 days after I bought the bike.

[cayuse60]

.....On later K75 there was a cup underneath the tank vents that would catch anything that came out of the vent tubes and then drain through a hose, but I gather yours does not have this. If you don't have the cup, a hose should be attatched to each of the two tubes and then routed to the right footpeg area.

Thanks...1991 K75 and it does have a cup with no drain line connected. Any excess fuel was being drained away to the top of the engine:eek

The plugged line is from the crankcase, the other line should have been connected to the cup?

Why have a cup?...just connect the excess fuel drain line directly to the tank connection NOT going to the crankscase.

[cayuse60]

It is not uncommon to take the vent hose that runs from the tank to the crankcase and disconnect it from the crankcase end and then run it to the right side by the centerstand. The thinking is that any fuel slosh caused by overfilling or any fumes caused by expansion will not find their way into the crankcase thereby compromising the oil. Usually these fumes gas off after the oil has been hot for a period of time. If you do alot of short trips (to the corner store, a close by friends house, etc,) it is thought that instead of gassing off, it builds up.

The two tank hoses (vent and filler overflow can be T'ed together if they go to the area of the right footpe(not left, there is a big chrome hot thing there!) But don't allow the filler overflow to go to the crankcase. If you overfill it , it will put raw gas into your oil.

You said that the hoses "were disconnected from THE FUEL TANK". On later K75 there was a cup underneath the tank vents that would catch anything that came out of the vent tubes and then drain through a hose, but I gather yours does not have this. If you don't have the cup, a hose should be attatched to each of the two tubes and then routed to the right footpeg area.

The little plastic funnel that clips to the frame under the tank is called an "air accumulator" and the part # is: 16 13 2 307 467. It positions under the two stub pipes on the tank.

The vent hose running from the tank to the crankcase was disconnected because it was one of those stupid ideas that didn't work out. Fill the tank, and park in the Sun on a warm day, and you were almost guaranteed to dump raw fuel into the crankcase - thus diluting the oil and trashing the bearings. My dealer disconnected this hose and installed the air accumulator (funnel) on my K75 back in '86 at the 600 miles service, 3 days after I bought the bike.

Thanks Paul....kind of thought the crankcase line was one of those CA emissions issues

---tim

[deilenberger]

Thanks...1991 K75 and it does have a cup with no drain line connected. Any excess fuel was being drained away to the top of the engine:eek

The plugged line is from the crankcase, the other line should have been connected to the cup?
If "the other line" is one that goes to the ground.
Why have a cup?...just connect the excess fuel drain line directly to the tank connection NOT going to the crankscase.It allowed BMW to have two functions for one line. The tank vent/overflow is only one - the other fitting on the bottom of the tank is the rain-water drain for around the fuel cap. Having both going into the funnel allows you to have both through one hose.