Fuel tank pressure

[quickdraw]

Out for a ride today and stopped for fuel after about 30 miles. When I opened the fuel tank, pressure (and a small amount of fuel) blew out. Never happened before, is this a common problem and what should I do to fix? :scratch

[roncooper]

The tank vents through a small hose at the right rear of the tank. There are two hoses at this location. One drains the hole you see at the left of the gas cap and the other vents the tank.

The only time mine has done this was after installing the tank, I pinched the hose.

You can buy a collecter from BMW that fastens to the frame rail and catches fluids/vapors that come out of the pipes on the tank. A hose then drains to the right foot peg area.

[quickdraw]

Ron

Thanks for the reply. I have the BMW accumulator (funnel) but have been waiting to install the next time the tanks was removed. Tank hasn't been off for months so I'm skeptical about a pinched line. Probably a plugged vent or drain as I get water from washing or rain collecting around the fuel fill cap. Any hints on clearing the lines and btw do both the drain and vent run to the accumulator or just the drain line.

[PGlaves]

Ron

Thanks for the reply. I have the BMW accumulator (funnel) but have been waiting to install the next time the tanks was removed. Tank hasn't been off for months so I'm skeptical about a pinched line. Probably a plugged vent or drain as I get water from washing or rain collecting around the fuel fill cap. Any hints on clearing the lines and btw do both the drain and vent run to the accumulator or just the drain line.

You can clear the drain by poking a wire through the tubing top to bottom. The vent itself is more problematic because the top of the vent line inside the tank is hard to access. I'd try compressed air from the bottom side.

[quickdraw]

Paul, thanks

There are 2 lines at the rear of the tank...the most rearward has a clamp on it (assume this is the vent) the other is just a slip fit (no clamp, or missing) I suspect this to be the drain. Both of the lines terminate along the swing arm so if plugged it could be anywhere along the route. A wire through the drain (working down from the top) makes sense but if i blow air up through the vent am I risking blowing what ever is in the vent line back up into the tank? May have answered my own question...sounds like removing the lines from the bike to clear and only dealing with the wire and air at the tank is the correct solution. Sound right?

[PGlaves]

Paul, thanks

There are 2 lines at the rear of the tank...the most rearward has a clamp on it (assume this is the vent) the other is just a slip fit (no clamp, or missing) I suspect this to be the drain. Both of the lines terminate along the swing arm so if plugged it could be anywhere along the route. A wire through the drain (working down from the top) makes sense but if i blow air up through the vent am I risking blowing what ever is in the vent line back up into the tank? May have answered my own question...sounds like removing the lines from the bike to clear and only dealing with the wire and air at the tank is the correct solution. Sound right?

Yes - remove the hoses first. Make sure they are clear. Then deal with the tubing running through the tank if necessary.

[58058D]

Not sure if the 75 had it, but my 85 100rs had an in line pressure 'valve' that would make a funny squeel when the pressure built above that and bled off that pressure. I believe this was a oneway valve so for sure you want the lines off it it is still installed.

Jim
Mendocino

[roncooper]

You may have an insect in the vent tube. If you have a MITY-VAC Etc you might be able to pull the obstruction out through the bottom of the vent tube.

I put a collecter funnel on my bike and took it back off due to smelling fumes.

[quickdraw]

Well...spent the afternoon working on the bike instead of riding (hate it when that happens) it was a beautiful day today. Unclipped the fuel tank and moved it rearward enough to block it up and work from under it (what a PITA). The small line (drain) was pinched. I used some braided picture hanging wire and tried to feed it down through the drain hole to try and clear the line inside the tank. Couldn't get it to feed all the way through to exit the smaller outlet below the tank. Installed the collector, ran a short length of the drain line to it and connected the balance to the remaining line that exits behind the foot peg bracket. Hope that problem is fixed.
Removed the vent line (larger of the two) tried blowing air up through the bottom however didn't notice any progress. I put everything back together and ran the bike for about 10 Min's. Opened the tank w/ no escaping pressure. Not sure if I accomplished anything with this portion of the problem. :dunno