Vanishing fuel...

[Air Ready Auto]

So it has been raining a lot here and I haven't put on many miles these last few weeks. I've noticed that when I park Lucy for any length of time her fuel level drops. Back when it was sunny and I could ride every day, I was filling up once a week. The last time I parked her she had a full tank and 3 days later when I hopped on she was down to about a half gallon. She is garage parked so no one is stealing it. I tested it by filling her up and letting her sit. After- 24hr down half gallon, 48hr down gallon and a half, 72hr down to half gallon in tank. She did not drop any lower than a half gallon. There is NO smell of fuel or fumes and no wet spot on the floor. No one else has the keys so my wife isn't out joy riding behind my back. I filled her up and twice a day I started her up or rode her to work and home. No significant fuel loss for 3 days while I did this. So where is the fuel going when not in regular use? Is there some kind of gremlin that drinks it from neglected ventures? Help please....

[CaseyJ955]

Tha tank being lower than the carbs sort of rules out needle valves and shutoff, and much of the plumbing. If you carefully inspected all the hoses and junctions my money is on a tank that has corroded from the inside out. Ethanol tainted fuel can expedite this with moisture content.

 

Possibly a hole small enough to weap but evaporate before it hits the ground and likely even make it difficult to catch a lung full of petroleum funk. I'll bet a pinhole in a hard to see place but if it leaks down to the last .5 gallon its close to the bottom, again assuming all hoses are serviceable. Maybe get a fiesty LED flashlight and have a look inside and around the lower outside of the tank. Please follow up when you figure it out, I'll be curious.

 

To further stretch my silly theories, maybe during regular use the normal fuel consumption leaves a vacuum in the tank preventing an external leak until vacuum is eventually dissipated allowing an external leak to resume, as the fuel tank vent could be obstructed and why no fuel loss under normal regular use. There, thats as far as I can reach haha. I hope you get it sorted soon.

Edited September 8, 2016 by CaseyJ955

[Flyinfool]

First place to check is the oil. Is the oil level still at half or below on the sight glass?

 

I had that gremlin visit me to until I kicked him out, I guess he headed north.

 

I never did figure out where he was putting the gas. But after a few tanks he quit.

[Air Ready Auto]

First place to check is the oil. Is the oil level still at half or below on the sight glass?

 

I had that gremlin visit me to until I kicked him out, I guess he headed north.

 

I never did figure out where he was putting the gas. But after a few tanks he quit.

 

 

The oil level is about 2 or 3 hairs above the lower part of the sight glass. That's another gremlin I have. I add oil to half way on the sight glass then it disappears down to there. It doesn't leak oil and doesn't burn it and never drops below that...

[Air Ready Auto]

Tha tank being lower than the carbs sort of rules out needle valves and shutoff, and much of the plumbing. If you carefully inspected all the hoses and junctions my money is on a tank that has corroded from the inside out. Ethanol tainted fuel can expedite this with moisture content.

 

Possibly a hole small enough to weap but evaporate before it hits the ground and likely even make it difficult to catch a lung full of petroleum funk. I'll bet a pinhole in a hard to see place but if it leaks down to the last .5 gallon its close to the bottom, again assuming all hoses are serviceable. Maybe get a fiesty LED flashlight and have a look inside and around the lower outside of the tank. Please follow up when you figure it out, I'll be curious.

 

To further stretch my silly theories, maybe during regular use the normal fuel consumption leaves a vacuum in the tank preventing an external leak until vacuum is eventually dissipated allowing an external leak to resume, as the fuel tank vent could be obstructed and why no fuel loss under normal regular use. There, thats as far as I can reach haha. I hope you get it sorted soon.

 

 

I have a stupid bright burn your eyes out LED flashlight I will try shining in the tank and see if there is any shine through. Genius idea my friend.

[Yammer Dan]

The 1st place these tanks rust out is around the petcock. My 86 did the vanishing fuel thing for a while and I came out one morning after filling it and garage floor was covered. Float was not sealing off and it ran it out the overflow.

[CaseyJ955]

Even if a tiny hole fails to shed light you can see if there is a corrosion problem, im away from home working so not sure if you can see the bottom of the tank from the filler neck. The next tool I buy will definitely be a borescope!

 

Im new to the VR so not sure how tricky it is to access the tank or what particulars are involved in pressurizing it a little and spraying the outside of the tank with a squirt bottle containing 4:1 water:dawn to spot pinholes in much the same way we find slow leaks in a tire. The tank should be dry for that and im not sure but maybe there is a fuel drainplug as on the vmax. Not sure if those or sending unit ports are subject to leaking. Theres no possible way your the first to deal with a suspected fuel tank leak so hopefully someone else who has can get more specific.

[CaseyJ955]

The 1st place these tanks rust out is around the petcock. My 86 did the vanishing fuel thing for a while and I came out one morning after filling it and garage floor was covered. Float was not sealing off and it ran it out the overflow.

 

I had an XS11 that did exactly that if I didnt turn off the petcock when not riding. I didn't know the Venture tank was high enough to gravity feed the carbs and drain out like that. I stand corrected.

[Flyinfool]

A full tank has the fuel level above the carbs. Once the fuel level drops to the level of the lowest float bowl the siphon will no longer happen. Since it is draining down to a half gallon left in the tank, the gas is all not coming thru the carbs. The par that puzzles me is that there is no gas smell in the garage with 5 gallons of gas evaporated in 72 hours, it should stink like gas real bad unless the garage is very well ventilated.

 

I'm still :scratchchin: :scratchchin: :scratchchin: :scratchchin:

[CaseyJ955]

A full tank has the fuel level above the carbs. Once the fuel level drops to the level of the lowest float bowl the siphon will no longer happen. Since it is draining down to a half gallon left in the tank, the gas is all not coming thru the carbs. The par that puzzles me is that there is no gas smell in the garage with 5 gallons of gas evaporated in 72 hours, it should stink like gas real bad unless the garage is very well ventilated.

 

I'm still :scratchchin: :scratchchin: :scratchchin: :scratchchin:

 

Ive had a few bikes that could have used new needles/seats and there was always a strong fuel funk when the carb/s overflowed. Seemingly anywhere its going if its leaking > 1gal/day it would smell of raw fuel. Are we absolutly sure the sender and gauge are reflecting acurate levels in the tank? Maybe park it with a full tank and measure physical level q4h with a flexable dip stick. At that rate of leakage its going to be wet somewhere. To rule out leaking through the carbs use a hose pincher or disconnect/plug the line feeding the filter and carb rack and see if your fuel loss is unchanged, with this you should be able to rule out carbs, hoses and filter and isolate it to the tank.

[snyper316]

Well I found where my fuel is going on mine, I have a clear filter and right where it is supposed to seal together is stained!! I just thought it was the summer Blends doing this. I don't have many dirt roads near me so the dust in the air has pointed it out to me! My metal ones never had this problem... But I wanted to see how my fuel was looking after derusting my gas tank. Seen this thread and looked at suggestions because I had a full tank and have only gone 43 miles and I am down to 2 bars.

 

DAMNED GREMLINS WILL EAT ANYTHING AND KEEP YOU VERY BUSY!!!!

[Air Ready Auto]

Ive had a few bikes that could have used new needles/seats and there was always a strong fuel funk when the carb/s overflowed. Seemingly anywhere its going if its leaking > 1gal/day it would smell of raw fuel. Are we absolutly sure the sender and gauge are reflecting acurate levels in the tank? Maybe park it with a full tank and measure physical level q4h with a flexable dip stick. At that rate of leakage its going to be wet somewhere. To rule out leaking through the carbs use a hose pincher or disconnect/plug the line feeding the filter and carb rack and see if your fuel loss is unchanged, with this you should be able to rule out carbs, hoses and filter and isolate it to the tank.

 

I'm positive it is reading properly because I went and filled it after day 3. The thing that is really confusing me is that with regular use there is no excess fuel loss.

 

 

Tried the super light with no conclusive results. The garage is 12X15 and kind of ventilated and like I said, there is no fuel smell. I will try pinching/plugging lines and see where that goes.

[gggGary]

Pull left covers and look for bubbled paint on the tank. Water sits in the low spots and rusts out the metal. I had an 83 that was slow leaking there, got lucky and found a rust free tank from out west, very reasonable. I was surprised how easy it was to swap tanks.

[Air Ready Auto]

Update on what I've done. I removed the tank and coated it in a product we use at the shop that goes on grey and turns muddy brown when exposed to petroleum products. I capped/plugged it and filled with gas. Let it sit over night and found it all grey in the morning. No leak in tank. Got it back together and was riding today and the clutch master cylinder went out... so fixing that next...

[Yammer Dan]

A full tank has the fuel level above the carbs. Once the fuel level drops to the level of the lowest float bowl the siphon will no longer happen. Since it is draining down to a half gallon left in the tank, the gas is all not coming thru the carbs. The par that puzzles me is that there is no gas smell in the garage with 5 gallons of gas evaporated in 72 hours, it should stink like gas real bad unless the garage is very well ventilated.

 

I'm still :scratchchin: :scratchchin: :scratchchin: :scratchchin:

 

 

And I've been thinking it drained the tank dry!! Just not thinking. Anywho it has sat about 6 months probally more like that!! Got a feeling I screwed up. Thinking it was dry I thought just put gas in it and fire up. Never thought about crappy gas sitting in it!! SOMETIMES I JUST DON"T THINK!! Got a feeling I'm in for some fun when I fire it up again. Battery was dying when this happened didn't have tags on it and........:bang head::bang head: CRAP!!!

[Flyinfool]

6 Months is not so bad.

Up here in the land of the SNOW machine it is normal for a bike to sit for 6 months at a a time. When I went thru my heart issues the bike got put up early in October, Never had a chance to do any PM on it for storage and was not able to ride it again until September of the following year. It sat for 11 months with a half tank of crap gas and no treatments in it. It ran a bit ratty for the first couple tanks of gas but it did run and the Seafoam did clean it out. 2 Months later I had to put it to bed for the winter again.

 

Get a battery and some Seafoam in there and crank it up.