Fuel overflows?

[mellowyellow9er]

I just so happen to fill up the tank, and when I start riding fuel started pouring out of the cap....WTF is this a common thing with the C109's. I've never had this problem with any other Suzuki's is it a bad cap or just "normal"with a too full fill up.

[STL-TIGER]

It's ok to stop adding gas on an odd number. Looks like you put in $16.00 worth and should have stopped at $15.69.

[Dirt2Street]

Im somewhat of a noob myself and the same thing happened to me about a month ago.. dont fill all the way and you'll be ok. you can find previous threads about this so we arn't the first ones..

[rynosback]

Do you fill your up sitting on the bike holding it upright or on the side stand?

[She's real fine my 109]

The weather matters a lot. If its hot out and the gas is in the grown and the temp is 45 and you just filled it to the neck and temps at 80. I WILL EXPAND

If i'm not going to ride I don't fill it to the neck. If i'm out riding i'll fill it to the neck and shake the put for a little more.

We had a guy on the forum that filled his bike on a hot day and parked the bike for the cool night with one of them chrome gas caps. The next morning his tank and collapsed.


Gas will expand and contract quit a bit more the anything else.

[holden,on]

it happend to me have heard of other c109r riders having the same problem

[mellowyellow9er]

I fill up with the bike on the kickstand.I know not to fill it all the way to the top,but damn they should have made the cap seal tight when the cap locks into place.

[Larry L]

I fill up with the bike on the kickstand.I know not to fill it all the way to the top,but damn they should have made the cap seal tight when the cap locks into place.

The fuel expands when hot, I have had it do it many times. Just try not to fill up to neck.
There was a company that made a cap that sealed tight. It was not vented properly & they had to buy a tank or two to people who bought their caps:)
Do a search for fuel tank collapsing.


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[mellowyellow9er]

It happens as soon as I take off from the station.It has nothing to do with temp the bike is not sitting in the sun.I just think they should have a different design on the fuel cap.Like I said before I've had plenty of Suzuki's and never had this problem,and I also know that I will not be filling it up that much anymore,but they sould have done some R&D on the fill ups.

[hunt1moore]

Cap is supposed to vent vapor not fluids. May need to check it.

[ELI]

It happens as soon as I take off from the station.It has nothing to do with temp the bike is not sitting in the sun.I just think they should have a different design on the fuel cap.Like I said before I've had plenty of Suzuki's and never had this problem,and I also know that I will not be filling it up that much anymore,but they sould have done some R&D on the fill ups.

Its simple, you are overfilling, this bike does not like to be filled completely, due to the wide, shallow tank design Suzuki went with because it looks cool. .Stop when its below the top to allow for expansion,it is easy to overfill.Everyone here has done it some refuse to admit it.

[Lemiarty]

I haven't...yet...but I bet it's worse in warmer areas.

[CDM76]

The weather matters a lot. If its hot out and the gas is in the grown and the temp is 45 and you just filled it to the neck and temps at 80. I WILL EXPAND

REALLY ? That'd be interesting to see .....
I expand too .... but usually around holidays, not weather dependant .....

[silveradols]

It was just overfilled. I over filled mine one time and it leaked. Now I stop when the gas is up to the bottom of the neck. So far I've had no problems since.

[jhorsf]

You will also notice a smell of fuel when you leave your bike in a locked garage put less fuel in stop when it gets to the filler neck bottom

[Pamm R]

My C109 manual says: kickstand down and don't fill past the lower neck. It says if you fill too much the gas in the neck cannot vent and is pushed out with pressure. Just like the pressure that builds up in a gas can with you remove the top.

[dugfir]

this has also happened to me , and it was not over filled but there was some white crusty residue on the rubber seal of the cap( 10% ethonol in the fuel ) , cleaned the cap and no problems.

[Captnpirate]

It's ok to stop adding gas on an odd number. Looks like you put in $16.00 worth and should have stopped at $15.69.

By the way, the cap needs to breathe otherwise you'd get a lock and then no gas to the injectors

[hunt1moore]

By the way, the cap needs to breathe otherwise you'd get a lock and then no gas to the injectors

If your lucky that is all it will do. Worse than that, the tank can implode (collapse) like a plastic gas can.

[bigdawg78]

I wanted to investigate how much gas expands. Sometimes I have bought gasoline early in the morning and by mid-afternoon in the southwestern desert climate, I notice that some gas has leaked out the cap. It could be that gas vapor is returning to a liquid phase after diffusing out of the tank valve (appearing as if it over flowed). Also when I over fill and take a right turn, it will pour out the valve. I've learned to put in less gas.

I was curious about the thermal expansion of gas due to temperature changes though. Looking up the thermal expansion coefficient I found it was approximately 5.278E-4/⁰F.

So, if you put in 4 gallons of gas (which is the most I ever put in), in the early morning (say 50 F⁰), and in mid-day it is 110 F⁰. The change in 4 gallons of gasoline is: 4 gallons * 5.278E-4 / ⁰F * (110 F⁰ - 50 F⁰) = 0.126 gallons.

I should note that the gasoline temperature inside the tank could get hotter as it is a confined enclosed space. It could be possibly be 150 F⁰ inside the tank. Just to be safe, let's double the number above to 0.25 gallons. So basically I should never put in more than 3.75 gallons in the morning if I expect a hot afternoon. Any more than that is asking for gasoline leakage should a large temperature change occur.

[mellowyellow9er]

Whoa, that was very technical and a hell of a way to say I over filled it.Thanks though.

[The HUFF]

I wanted to investigate how much gas expands. Sometimes I have bought gasoline early in the morning and by mid-afternoon in the southwestern desert climate, I notice that some gas has leaked out the cap. It could be that gas vapor is returning to a liquid phase after diffusing out of the tank valve (appearing as if it over flowed). Also when I over fill and take a right turn, it will pour out the valve. I've learned to put in less gas.

I was curious about the thermal expansion of gas due to temperature changes though. Looking up the thermal expansion coefficient I found it was approximately 5.278E-4/⁰F.

So, if you put in 4 gallons of gas (which is the most I ever put in), in the early morning (say 50 F⁰), and in mid-day it is 110 F⁰. The change in 4 gallons of gasoline is: 4 gallons * 5.278E-4 / ⁰F * (110 F⁰ - 50 F⁰) = 0.126 gallons.

I should note that the gasoline temperature inside the tank could get hotter as it is a confined enclosed space. It could be possibly be 150 F⁰ inside the tank. Just to be safe, let's double the number above to 0.25 gallons. So basically I should never put in more than 3.75 gallons in the morning if I expect a hot afternoon. Any more than that is asking for gasoline leakage should a large temperature change occur.

You forget that gas comes out of the ground at most stations. So especially if you fill up in the heat of the day, the gas has to go from 50 degrees t ambient temp very fast. so more will fit in a tank even when it's hot. That's what is causing the overfill. the C109 caps must be a little longer or something. Some how the breather hole is getting into the gas. I'd be curious to see what a C and an M cap look like beside each other.

[BlessThisNine]

I wanted to investigate how much gas expands. Sometimes I have bought gasoline early in the morning and by mid-afternoon in the southwestern desert climate, I notice that some gas has leaked out the cap. It could be that gas vapor is returning to a liquid phase after diffusing out of the tank valve (appearing as if it over flowed). Also when I over fill and take a right turn, it will pour out the valve. I've learned to put in less gas.

I was curious about the thermal expansion of gas due to temperature changes though. Looking up the thermal expansion coefficient I found it was approximately 5.278E-4/⁰F.

So, if you put in 4 gallons of gas (which is the most I ever put in), in the early morning (say 50 F⁰), and in mid-day it is 110 F⁰. The change in 4 gallons of gasoline is: 4 gallons * 5.278E-4 / ⁰F * (110 F⁰ - 50 F⁰) = 0.126 gallons.

I should note that the gasoline temperature inside the tank could get hotter as it is a confined enclosed space. It could be possibly be 150 F⁰ inside the tank. Just to be safe, let's double the number above to 0.25 gallons. So basically I should never put in more than 3.75 gallons in the morning if I expect a hot afternoon. Any more than that is asking for gasoline leakage should a large temperature change occur.

Uh wtf did you say?

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[mellowyellow9er]

The cap on my M looked alot like the caps on my sport bikes,they never leaked fuel no matter how low I leaned or if I was doing a wheelie with a full tank. You dont hear about those tanks imploding or leaking when it gets hot outside.

[victorr1]

The problem of odor and overflow from the fuel tank cap is on all of M and C
This is because the design does not provide for drainage of the neck of the overflow.For example Harleys and Yamaha, regardless of model, the neck has a drainage tubedrawn down as a sportbike.
Therefore, ventilation and drainage is carried out through the holes in the lid of the fuel tank.

So we just need to make drainage \ breathing hole

In the last few days thinking about this question. Came up with two ways to
A. Buy sportbike tank or chopper, which provides drainage of the neck. Welded into the fuel tank filler neck from C along with the full withdrawal of a drain at the bottom of the tank.
B. Welded into the fuel tank drain tube only. Externally, the fuel tank remains the same. Go to the inner wall of the neck welded 5mm thin metal tube that comes out from the bottom of the tank and it will wear down the rubber tube passing motorcycle. Fuel tank cap seal with silicone sealant.

I want to implement the second method in the next rainy season. It remains to find a qualified welder for thin metals.

[ace4aday]

I ride year round, in temps ranging from high 20-115F, and have never once spilled or leaked fuel when only filling to the neck (like the owner's manual tells you to do).

[funbuster19]

When my C was new, first two tanks both spilled. I learned my lesson, and stopped filling it so full.
Today coincidentally, I filled up, then got out of the way of an inpatient cager, and pulled out from under
the canopy into the hot sun. Bought a slurpee, came out and found gas running down the side That was quite some expansion. I wonder if the fill neck gets full of gas, then vapours expand pushing ful up and out? I wonder if a couple of holes near the top of the fill neck would let pressure equalize. Probably just a stupid idea, ..., just sayin

[delta579]

Met a guy at bike night with a C, like mine. He had the same problem with fuel "burping" out the cap. His solution was to drill 2 holes fore and aft in the filler neck to equalize the pressure in the filler neck with the rest of the tank. No "burping since then. The "neck" will force any fluid trapped inside itself UP and to the cap as the tank pressure builds from engine heat or ambient. No different than squeezing a plastic bottle with a draw tube in it.
He said he drilled the holes (1/8" dia.) as close to the top of the neck as he could get. He stuffed a rag tied to a string into the tank to catch shavings, then vacuumed the shavings out before removing rag. He used a balloon on the 2nd one and sprayed a light oil(WD40) on the balloon to "stick" the shavings to it. Deflated balloon, and pulled it out. He said both ways work.
Haven't done it to mine yet, but seems logical. I would definitely use a drill extension and have a fan blowing the fumes away from the drill, or use an air/hand drill.
Hopefully the fire dept. doesn't pay a visit when I do mine.

[CanadianM109R]

When my C was new, first two tanks both spilled. I learned my lesson, and stopped filling it so full.
Today coincidentally, I filled up, then got out of the way of an inpatient cager, and pulled out from under
the canopy into the hot sun. Bought a slurpee, came out and found gas running down the side That was quite some expansion. I wonder if the fill neck gets full of gas, then vapours expand pushing ful up and out? I wonder if a couple of holes near the top of the fill neck would let pressure equalize. Probably just a stupid idea, ..., just sayin

Thats actually a good explanation. If the bottom of the filler neck is submerged in the gas, the heat will vapourize and expand some of the gas in the tank, thereby pushing the liquid gas up the filler neck and eventually out of the tank. Drilling a small hole in the filler neck near the top (inside the tank) would likely allow the pressure to equalize in the tank, and it would allow the vapours to escape to the cap vent, stopping the problem. The best place to drill would be opposite the kickstand, so that when the bike is on the stand, this hole is at the highest point in the tank. (allow a professional to do this work if you don't know exactly what you are doing)

Discaimer: I am not an expert on this. Drill at your own risk. I assume no responsibility for people being dumbasses and drilling the top of their tanks from the outside, etc.

Obviously, the best way to prevent this is not to fill your tank to the point where the whole bottom of the filler neck is submerged.......problem solved.

[dre319]

Happened once to me as well. Was out riding with Swatcop and we just gassed up. Stopped for a bite and when we came out, I heard my tank hissing. I popped off the cap and it spewed everywhere.
I filled up to the neck of the tank and it was freaking hot out. Lessoned learned.