Dripping Gas (everyday) - Fuel Tank VENT hose.

schrecke · Jun 8, 2007

I've read all the posts about this happening on hot days occasionally, but my bike does this everyday, even when its 60 degrees out. Hoses are cut at an angle facing rearward.

I've disconnected and cleaned both the Fuel overflow and vent hoses. Reconnect to tank, and clean entire paths from filler neck all the way down using contact cleaner. Everything is clear. Removed cap and performed the cleaning service detailed on this forum. My little orange grommet that completes the path between gap cap and filler neck to vent hose is in place.

Should I really be leaving puddles of fuel everyday from the vent hose? Puddles are still wet after a work day and are about 5" in diameter.

I've verified that it is coming from the vent hose and not the overflow hose. This is happening at full tank or 1/8 tank and everywhere in between.

I remember reading a post about drilling a hole in the fuel cap plate to allow venting to occur due to extremely stiff springs in the lid preventing normal operation and riders getting sprayed in the face upon opening the cap. This doesn't seem to be my issue I don't think.

Ideas? :blink:

radman · Jun 8, 2007

If they're still wet after a day, it's coolant, not fuel. Antifreeze will not evaporate, at least not for a very, very long time. The fact that you see this regardless of tank level confirms-the tank won't vent raw fuel if it's not able to reach the filler opening. Most likely the coolant reservoir is overfull, or you have a bad rad cap,, or the cap isn't fully seated, or a bad head gasket. The other possibility is that you have a coolant leak somewhere, and it only appears that it's coming from a vent hose, as you state the liquid isn't coming from the reservoir hose (right side of bike, exits near the coolant pump).

Geezer · Jun 8, 2007

It has been my experience that once fuel drips out of the overflow onto asphalt, there will be a stain that looks like it is still wet. That stain will take months to disappear, if ever. So, I assume that you are not parking in the same place, over the same stain everyday. You may have a minor fuel leak coming from somewhere other than the overflow hose.

I suggest that you place some absorbent paper under the bike, and let it catch the leak. Newspaper will probably do the trick. Then you can see from the color and smell if it is fuel, oil, or coolant.

Ignacio · Jun 8, 2007

Just to be clear....one of those three vent lines must not be fuel? I've traced down two of them totally as fuel, but that third one eluded me. But one of them is coolant? If so, that just makes total sense and a minor personal mystery resolved!

Bounce · Jun 8, 2007

yep. one's the overflow tube from the overflow tank from the radiator cap from the radiator.

Ignacio · Jun 8, 2007

Thank you Mr. Bounce Sir. Minor mystery resolved. Because I couldn't figure out that third line I was second guessing an aux. fuel cell issue as being vent related.

radman · Jun 8, 2007

Ignacio said:
Just to be clear....one of those three vent lines must not be fuel? I've traced down two of them totally as fuel, but that third one eluded me. But one of them is coolant? If so, that just makes total sense and a minor personal mystery resolved!

Left side-one is filler neck drain (spill drain), one is tank venting, one is air cleaner box drain. Right side is coolant overflow (reservoir overflow).

schrecke · Jun 8, 2007

Like I said I traced and removed the two fuel tank hoses that route down the left side of the bike and exit near the U-Joint along with the airbox hose.

I marked the overflow hose with tape and have verified that the drip is coming from the one that I think is the vent hose. Of the two that connect to steel nipples on the left side of the tank, the one in question is connected to the nipple closer to the seat.

The puddle is nowhere near the coolant hose which peeks out along the right side of the bike much further forward than the other 3 hoses.

My puddle sure smells of gas, unless is just mixing with old gas and crud on the ground.

I'm going to go re-verify all this out in the lot right now.

Oh yeah, and before someone asks, is an 05 ABS w/ ~5K on it.

Low miles, I know, but I just picked it up used this spring.

odot · Jun 8, 2007

You can make sure it's gas by trying to set it on fire with a lighter.

radman · Jun 8, 2007

One other possibility is a failed seal on the gas cap. This could allow fuel to splash into the filler area, which would then drain from the hose. There is also a check ball in the filler cap, which, if stuck closed (it's an anti-spill device in the event of a tipover), could cause the tank to possibly vent through the overflow, though thats a stretch. There's no good reason for a constant flow through any of the vent lines, unless a crack or bad weld exists on the vent tube. Or, the vent tube has a crack or bad weld that is causing a tank leak, and the fuel is simply wicking along the hose.

schrecke · Jun 8, 2007

radman said:
One other possibility is a failed seal on the gas cap. This could allow fuel to splash into the filler area, which would then drain from the hose. There is also a check ball in the filler cap, which, if stuck closed (it's an anti-spill device in the event of a tipover), could cause the tank to possibly vent through the overflow, though thats a stretch. There's no good reason for a constant flow through any of the vent lines, unless a crack or bad weld exists on the vent tube. Or, the vent tube has a crack or bad weld that is causing a tank leak, and the fuel is simply wicking along the hose.

Thanks for all the info Radman.

I just verified. Its been in the lot since 8am, its just got into the low 70's degrees here in MA. Currently have a small stain, the end of the hose is wet and currently dripping. Unless I marked the hosing incorrectly, its coming from the Vent, not the overflow. Its definitely gasoline, and its definitely coming out from inside the hose, not wicking along the outside of the hose.

Note that it does not do this when parked in my garage, and I don't think its done it at temps below 60's. I think that would rule out a crack in the steel portion of the line inside the tank, no?

:huh:

Constant Mesh · Jun 8, 2007

When the bike is sitting out in the sun the gasoline vapor in the tank will get quite hot no matter if the ambient temperature outside is not all that high. When the bike is sitting in a shaded area the vapor is no hotter than the ambient temperature.

The sun heated hot vapor condenses as it travels out through the cooler vent hose.

The FJR's metal fuel tank is quite large and totally exposed to the sun. It absorbs a lot of radiant heat from the sun.

radman · Jun 8, 2007

Constant Mesh said:
When the bike is sitting out in the sun the gasoline vapor in the tank will get quite hot no matter if the ambient temperature outside is not all that high. When the bike is sitting in a shaded area the vapor is no hotter than the ambient temperature.
The sun heated hot vapor condenses as it travels out through the cooler vent hose.

The FJR's metal fuel tank is quite large and totally exposed to the sun. It absorbs a lot of radiant heat from the sun.

Makes perfect sense, 'cept Frank has never done this, full or 1/8 or whatever. They must have some exceptionally volatile fuel Maryland way.

schrecke · Jun 8, 2007

radman said:
Constant Mesh said:

When the bike is sitting out in the sun the gasoline vapor in the tank will get quite hot no matter if the ambient temperature outside is not all that high. When the bike is sitting in a shaded area the vapor is no hotter than the ambient temperature.
The sun heated hot vapor condenses as it travels out through the cooler vent hose.

The FJR's metal fuel tank is quite large and totally exposed to the sun. It absorbs a lot of radiant heat from the sun.

Click to expand...

Makes perfect sense, 'cept Frank has never done this, full or 1/8 or whatever. They must have some exceptionally volatile fuel Maryland way.

This sounds logical enough, but if it were the cause I would expect most if not all FJRs to do the exact same thing. This cannot be expected by design...

BTW, MA != Marlyand, but doesn't really matter.

I'd be ok with a drip or two, but not this.

odot · Jun 8, 2007

Well, get it fixed or I'm calling the E.P.A. on your ***.

Geezer · Jun 8, 2007

schrecke said:
This sounds logical enough, but if it were the cause I would expect most if not all FJRs to do the exact same thing. This cannot be expected by design...BTW, MA != Marlyand, but doesn't really matter.

I'd be ok with a drip or two, but not this.

Mine does this once in a while. I first noticed it after I filled the tank just before I got to work on a sunny warm day. It happened last week with about 3/4 tank. Thinking about it now, I would say it happens on days when it is cool in the morning and then warm and sunny later. It never happens in the garage, even with the tank topped off.

schrecke · Jun 8, 2007

odot said:
Well, get it fixed or I'm calling the E.P.A. on your ***.

You won't have to. With the prices like they are I'll have to start catching the drips and putting them back in the tank

RonBB · Jun 8, 2007

It absorbs a lot of radiant heat from the sun.

Picks up a lot of engine heat as well while riding. I assume that the garage parking is level. Is the other location level? center or side stand? Same at both locations? Just a thought & possible other data points. Best of luck.

schrecke · Jun 8, 2007

RonBB said:
It absorbs a lot of radiant heat from the sun.

Click to expand...

Picks up a lot of engine heat as well while riding. I assume that the garage parking is level. Is the other location level? center or side stand? Same at both locations? Just a thought & possible other data points. Best of luck.

Garage is level. Parking at work where I notice this is a concrete pad with a very slight uphill grade. I park the bike facing up the hill and leave it on the sidestand.

Dripping Gas (everyday) - Fuel Tank VENT hose.

Help Support Yamaha FJR Motorcycle Forum:

Well-known member

R.I.P. Our Motorcycling Friend

Parsimonious Curmudgeon

Intramural Culture Warrior

Chicks Dig Scars

Intramural Culture Warrior

R.I.P. Our Motorcycling Friend

Well-known member

CC member # 17,----- DUP member # 7, mensa club m

R.I.P. Our Motorcycling Friend

Well-known member

Well-known member

R.I.P. Our Motorcycling Friend

Well-known member

CC member # 17,----- DUP member # 7, mensa club m

Parsimonious Curmudgeon

Well-known member

Well-known member

Well-known member

Similar threads

Join the conversation!

Join today and get all the highlights of this community direct to your inbox. It's FREE!