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Discussion Starter · #1 ·
It's been this way for quite a while now as in maybe over a year. The sniff test over the cap always smells like fresh gasoline all the time and if I set my helmet over it in short order it's permeated the liner of the helmet to smell like gasoline. I did tighten up the 6 bolts on the ring which made no difference, and it would appear the gasket seal on the inside of the filler cap seems okay. How might this be repaired?
 

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I have the same bike with a tank bag on all the time. Can't smell anything. So I went out and checked the cap and all there is, is a black and red rubber gasket. So I stuck my nose on the tank and I can smell fuel. Its not real bad but it I left a helmet on it for awhile it might smell.
 

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Mine would do that on occasion. Found it was not latching fully. Put some lube on the latch parts and a light film of vaseline on the seal. Done that a few times over the years. I have a manual lock, not keyless, so not sure about the differences.
 

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Well, this is just a wild idea. I haven't had the tank plastics off my 2018 RT yet, so I don't know what, if anything is under that "hood". I'm not even sure if I ever stripped my old hexhead RT. But back when I had an R1100RT-P, when I did pull off the plastic, there was another opening on the tank, i.e. honestly can't recall what it was. Wasn't for an in tank fuel pump. Maybe the fuel level sensor?

Anyhow, my point is, if there is another opening in that tank where your gasket has failed, the fumes you smell may be coming up through the top of the plastics, exiting near the filler neck. I'd pull the tank completely off an inspect it. If you're smelling fuel vapors, it IS coming from somewhere on that tank. (Of course, you could also always bring up a microfiche or service manual and look before you leap, but I usually think of that kind of stuff AFTER I've ... er... leaped.) There's also a recirculation system from the gas canister, and any hose leak from the canister back to the tank could cause your problem. (A common problem with vehicle owners is overfilling the tank. Overfilling can flood your carbon canister, which is designed to trap those gas tank vapors, or even dump fuel on your air filter box (or, again, my memory is poor, maybe that only applied to the oil heads. NEVER top off your tank all the way to the top)..

re: " it would appear the gasket seal on the inside of the filler cap seems okay. "

"Seems" and " appear" mean nothing. Yes and No mean something. All it takes is a pinhole gap somewhere in that gasket, then you've got you leak, and you can crank that tank ring until you strip out the screws and it won't solve your problem.

I also don't know what it would take for the gas cap itself to fail, or what that would observably look like. If I pulled the tank, and saw nothing obvious other than the tank neck area (which could even be cracked, ya never know), I'd probably next try to test by sealing up the top with saran warp, or something like that, then take a fresh cloth and set it up on top for a couple of days. At least then, I'd know that the leak source was DEFINITELY in the neck if there was leakage, or not, if the terry towel still smelled like fuel.

Not great answers, but it's kind of a complex problem. The best way to solve complex problems is to break it down, break it apart, and test each subset (or subsystem). Again, this is just some "wild ideas" to give you a bit of a framework in which to "debug" your problem (Yeah. 🙄 I once was a computer guy, too ....).
 

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Discussion Starter · #5 ·
Thanks all. I am very guilty of topping off my fuel fills so probably I've saturated the charcoal filter. How is that replaced, if it can be? And apparently, I'm not alone on this!

I checked the filler cap's rubber gasket and is in way too good condition to cause any issues. It takes some pressure to push down and latch it so I would be surprised if it isn't sealing there. I can try a thin coating oil to seal it and see if it helps as a test. I did put packing tape overtop of the filler cap but inside of the outer hold-down ring, to isolate the ring from the cap as a source, and it seems a little better for sure, but still very detectable gas odor. I bought a replacement gasket for the outer ring but that requires removing the plastic trim (as you would do for an air filter change, god help me...). My plan right now unless sealing the filler cap ring fixes it is to go ahead and replace it though dang it I replaced the air filter only 2K miles ago, and it DOES NOT get very dirty where I live and ride now at so I only change it every 24K miles.

Thanks again!
 

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Thanks all. I am very guilty of topping off my fuel fills so probably I've saturated the charcoal filter. How is that replaced, if it can be? And apparently, I'm not alone on this!

I checked the filler cap's rubber gasket and is in way too good condition to cause any issues. It takes some pressure to push down and latch it so I would be surprised if it isn't sealing there. I can try a thin coating oil to seal it and see if it helps as a test. I did put packing tape overtop of the filler cap but inside of the outer hold-down ring, to isolate the ring from the cap as a source, and it seems a little better for sure, but still very detectable gas odor. I bought a replacement gasket for the outer ring but that requires removing the plastic trim (as you would do for an air filter change, god help me...). My plan right now unless sealing the filler cap ring fixes it is to go ahead and replace it though dang it I replaced the air filter only 2K miles ago, and it DOES NOT get very dirty where I live and ride now at so I only change it every 24K miles.

Thanks again!
I've picked up codes on my Ford Edge when it was overfilled. It eventually self-corrected, i.e. the canister dried out when the idiot stopped overfilling his tank. 🙄😖 I suppose the canister can be removed and dried out (blow some air through it, etc.), and there are internet links to that effect.

Then there is this option:
Removing BMW tank carbon canister

Disclaimer: I haven't done this on my bike(s), but I agree with the gentleman's sentiment, and will do so if I have any problems with it. The folks demanding this stuff be added to US bikes are neither rocket scientists nor automotive engineers. The goal of such people is largely to degrade, and eventually (forcibly) remove all combustion engines from the earth. Hence, their reasoning of preventing the minor fuel vapor loss from a motor vehicle from entering the atmosphere, are neither rational nor reasonable to me. They do not have the best interests of me or my machine, at heart. /end rant.
 

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Actually evaporation from fuel tanks nation wide used to contribute to over all air pollution. Along with the vapor released when you fill up. I agree those canisters on a bike can be a pain. And contribute to a couple failure modes if filled with fuel. I don't over fill and all goes well. But I have had to by pass them on other bikes just to get the bike running more than a few minutes. The vacuum created in the fuel tank when the thing is clogged will shut a bike down. I like them because it keeps the gasoline smell out of the garage. I have removed them from past bikes I have owned though. My 09 K bike has its original canister.
 

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Discussion Starter · #8 · (Edited)
It's external to the tank and easily accessible on the oil head. I'm wondering how that could be the source of fumes coming out of the cap area?

I went back to sniff around the retention ring, with everything inside of the ring sealed w/ packing tape, and I can def smell gas along the ring edges, so perhaps that gasket is no good--I can't imagine why it would have failed though.
 

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Hi everyone and following this lead me down a recent path whereby my fuel gauge reads a over a 1/6th of gas and I'm out of gas. My year is 2007. so this winter it'll be to get get the pump assembly out and serviced/replaced etc. Question is if overfilling is a bad thing is this related to my recent walking for gas?
Thanks
Bill
 

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Hi everyone and following this lead me down a recent path whereby my fuel gauge reads a over a 1/6th of gas and I'm out of gas. My year is 2007. so this winter it'll be to get get the pump assembly out and serviced/replaced etc. Question is if overfilling is a bad thing is this related to my recent walking for gas?
Thanks
Bill
I could be wrong, but I believe the hexheads were notorious for the fuel level strip failure (i.e. a strip inside the tank that measured and transmitted fuel level). It's not a cheap fix, and it doesn't stay fixed. Search the hexhead (2005-2009 R1200RT's) forum here and on bmwst.com, for related info. It's unrelated to overfilling and gas in the carbon Evap canister.
 
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