Gasoline is dripping out of a rubber tube outputting on the bottom of my motorcycle - is this normal, or is it a problem?

Question

What bike?

A BMW 650, 1996 model.

What's the problem?

I noticed a slow, but steady, drip of gasoline from one of two rubber tubes that output to the bottom of the bike. I think the other rubber tube is there to take water away from the carburetor, it drips water if I ride the bike on really hot summer days.

Gasoline is dripping out of one of the two tubes.

Additional context

I've just taken the bike back out of storage, and refilled it with oil and gas, as well as putting a fully charged battery back in. For some reason, it's refusing to start - I don't know if the not starting problem is related, that's not what worries me. I'm worried to see gasoline drip out of a tube, when I don't know what the tube is for. Maybe I flooded the engine with fuel and this tube is there to drain it?

Answer 1

On most bikes the carb has an overflow port that drains through a tube to the ground. This is important if the float sticks. Usually you can tap the float bowl with a screwdriver and unstick it, but if it happens again, overhaul the carbs.

Also, don't smoke around a bike that's dripping gas.

Answer 2

My bike does this every couple of years after storage over winter. I have found that the float obsorbs some fuel and thus the level overfills. I have adjusted it some (hard to get right on mine) but the best bet for me was to replace the float.

Either way, it should NOT drip or leak fuel. I have not seen any BMW at the shop I worked at leak except as I described above.

Oh, just to be clear, mine is an R60/6, so a bit older - and it has a rigid foam float as a stock item. If yours is a BMW it should have a petcock - I make a habit of closing mine after every ride as sometimes heat changes will cause fuel to leak.

I don't park on the side (ride off kickstand keeps it level) but I have a friend who does sometimes and it will occasionally do a small drop if he does not close the petcock.

EDIT NOTE: ensure that this is NOT from a cracked fuel tank. You don't say if this is an R series or the F series (looks like an F series from the picture though). I think there was a recall on the F series tank at one point.

Also note the Fuel Injected bikes (GS, Dakar, CS, G650X) have pressurised fuel lines. When you turn the key to the on position, you should hear the fuel pump pressurising the line. Just after you turn the bike off the fuel line will still be under pressure.

Is this leak just during riding or while it is stopped? Will it leak just after you stop also? The pressure might last quite some time if that is the case and a small leak might be detected for a bit after you turn off the ignition. You might need new clamps and a fuel line in that case. I would recommend having a qualified service tech replace those in that case.

Try removal of the seat, looking at the fuel system with the key on to see if you see leaks/fuel pooling there as that might also occur - keep in mind the fuel is pressurized for the injectors.

Final note: there have been some fuel system recalls on the F series - you can search for those with your specific model number as well.

http://faq.f650.com/FAQs/ServiceBulletinsFAQ.htm

Answer 3

Does that model have a petcock? Perhaps you just need to turn the gas off when you park?

Answer 4

I believe this may well be a vent/overflow line to the fuel tank. How full is (was) your tank at the time? My K75 (fuel injected, unlike yours) has this arrangement. If this is in fact the case, the bike was likely performing as designed.

Answer 5

According to the answers I got on my question: "What are these hoses sticking out", that rubber hose is a fuel tank overflow hose.

"A very full fuel tank can sometimes overflow a bit because of heat and sloshing around". "the overflow hoses are there to channel gasoline (...) away from the rider and onto the ground so you don't start on fire or get severe burns. They are a good thing™" (GdD, 2020)