GL1100 gas cap and vacuum

6744 Views 25 Replies 15 Participants Last post by ThFireman, Nov 2, 2009

Bschofield

Discussion Starter · Jul 31, 2009

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After definitively verifying that i am definitely getting a vacuum in my tank (by starting to cut out on the expressway and opening the gas door while at speed and removing the cap on two different occasions recently) and after soaking in seafoam, beating the rust and crud on multiple occassions. tonight i am going to do the following, and take pictures if others want to do the same.
I am going to drill 2 holes in my cap, I am going to insert 2 one way back-flow prevention aquarium valves that i picked up from wallyworld. i am going to probably JB-weld them in place.

my expected results are that i will no longer have a vacuum buildup in my tank, and i will not have to worry about fuel or vapors escaping...

just an fyi, and maybe some insight..

ps. I know i can buy another cap, but this will cost me about $2 to do.. and besides.. by the time i'm done this bike isn't going to look stock anyway!

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1 - 20 of 26 Posts

sandiegobrass

· #2 · Aug 1, 2009

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Why bother with the valves... just drill a small hole... cars/bikes have run for 70 years without it.. that is just a vapor emissions issue.... I have even forgotten to put the cap on until the next fillup and didn't notice anything...:shock: (unless you have to have your cap checked for emissions testing.. but not even California does this for motorcycles)

Bschofield

Discussion Starter · #3 · Aug 1, 2009

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i guess i just don't like the smell of gasoline.. hehehe.. it's the paranoid in me.. i smell gas and i immediately to a bike check.. gas lines.. check. fuel pump check, carb bowls check.. hmmm ok.. no fires right now.. must be my tank..

brianinmaine

· #4 · Aug 1, 2009

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I used like a 1/8" bit, works fine, lasts long time!

keithg64

· #5 · Aug 2, 2009

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I just took off the rubber gasket and will try that for a couple of days and see how that works. Seems like the cap fits loose but I don't think it will come off, but we'll see.

G

· #6 · Aug 2, 2009

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Drill a hole in it and put a cotterpin in the hole so that it can catch air and not let gas out, bend the clip on the inside so it wont come out.
You have a vent and nothing can go into the hole.

kyboy67

· #7 · Aug 3, 2009

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Humm,I put my gas cap on crooked and it ran fine down the interstate,but once pulled up at a light and went to take off and the bike acted like it wasn't getting enough fueland would die.it would start back up but would barely run,after I found the cap on crooked and fixed it,it started right up and never missed a beat since.

jar

· #8 · Aug 3, 2009

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I thought the gas tank was suppose to have vacuum

GOD Bless,
jerry

morriscatt

· #9 · Aug 3, 2009

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kyboy67 wrote:

Humm,I put my gas cap on crooked and it ran fine down the interstate,but once pulled up at a light and went to take off and the bike acted like it wasn't getting enough fueland would die.it would start back up but would barely run,after I found the cap on crooked and fixed it,it started right up and never missed a beat since.

I'm pretty sure there is a thread that discusses the 1500's and up needing pressure in the tank. they say you should hear air escaping when you take the cap of your bike.. Where as when I had this problem on my 78, the plugged cap caused a vacuum and did not let gas flow. Air would swoosh into the tank when removing my cap.. so I cut a slice in my gasket put it back on and it has been fine since.

Bschofield

Discussion Starter · #10 · Aug 3, 2009

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update: i did as suggested instead of my hairbrained idea.. just drilled two eigth inch holes.. awesome.. no more vacuum.. and yes. when a chamber loses contents (ie tank) the contents must be replaced with something, usually air, and if that can't happen on a gravity feed manual fuel pump driven vehicle, you get no fuel flow.. and i am free of that! yes.. thank you all for your suggestions.. :clapper:

corventure

· #11 · Aug 4, 2009

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Glad to hear. I was just about to warn you that the aquarium valves would have likely fallen apart from the fuel and fumes of gasoline!!!!!!!!!

Bschofield

Discussion Starter · #12 · Aug 4, 2009

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that was actually a concern of mine as well. and to address my other concern of smelling fumes.. surprisingly after 2 tanks,, no smell of gas..

jar

· #13 · Aug 4, 2009

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Is my 1200 not suppose to have vacuum in the tank or is that just on the 1500 (FI)

keithg64

· #14 · Aug 5, 2009

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jar wrote:

Is my 1200 not suppose to have vacuum in the tank or is that just on the 1500 (FI)

I beleive it to be the 1500 and up, the 1200 run off the same principle as the 1100.

FixRupR

· #15 · Aug 5, 2009

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I took off my cap last night when it started missing and it did help. I ride an 83 gl-1100. My fuel filter runs almost completely empty all the time and the bike misses in the upper rpm's. There is always a vacuum hiss when i open the gas cap. It's got a mechanical fuel pump. I wonder if drilling a hole is a good idea or should I be looking for some other problem. hmmm....

rgbeard

· #16 · Aug 5, 2009

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Is someone saying that the 1500s are FI?

Which ones?

Bschofield

Discussion Starter · #17 · Aug 5, 2009

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FixRupR wrote:

I took off my cap last night when it started missing and it did help. I ride an 83 gl-1100. My fuel filter runs almost completely empty all the time and the bike misses in the upper rpm's. There is always a vacuum hiss when i open the gas cap. It's got a mechanical fuel pump. I wonder if drilling a hole is a good idea or should I be looking for some other problem. hmmm....

since i drilled the holes in mine over the weekend.. i have gone through 2 tanks and most of it freeway.. runs awesome.. i would always start leaning out around 2/3 of a tank and now .. performance is the same.. drill away man! if you don't like it get a new cap! at least you will eliminate it as a problem!

FixRupR

· #18 · Aug 12, 2009

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I removed the rubber ring from my cap like Kiethg64 and rode all weekend and it definitely ran much better. I was able to go through a couple of tanks of gas and was able to ride at any speed. This is not safe in case of a fall but was good proof that I should probably pick up a different cap or perhaps try the cotter pin method. Good thread :goofygrin:

keithg64

· #19 · Aug 12, 2009

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I never thought of the fall thing but that is a good thought, I also thought that the cotter pin thing was a good idea but just taking the rubber ring off was a quick fix.

Bike...and Dennis

· #20 · Aug 12, 2009

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Just a note Bschofield. At the emission station by the Glendale Airport,they do look at the gas cap.

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