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R1100R Fuel filler cap suction


kalali

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Hello folks, this is probably a newbie question and I did a search with no luck. I've noticed that in my new(to me) R1100R (with 16000 miles) I have some suction when I open the gas cap. It's a lot more pronounced if the tank is low on gas but it's still noticeable even after 60 miles from full tank. I don't know if this is normal or it's a symptom of some obstruction in the in the vent hose(es) and/or charcoal canister. I've read/seen about folks removing the canister so any advice is appreciated. From the engine performance perspective, the only behavior I've experienced is a little rough starting when the bike when it is cold but otherwise I can't tell if the motor is starving from fuel anytime during normal riding after warm up. The only reference I have is that the fuel vent hose in my Buell vents to atmosphere. Thanks and sorry if this has been discussed earlier.

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Sounds like classic blockage to the evap system - could be somewhere in the lines but likely the canister itself. Easiest solution is to remove the canister and vent the tank to atmosphere. This will allow fuel vapor to escape intead of being returned to the tank; no performance issue but some consider it to be an environmental issue. My understanding is that only US models of your bike had the canister system.

 

Search here, or just google R1100R canisterectomy for lots of info.

josh

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Don't want you to panic, but the vacuum created by the blocked vent hose can get pretty strong. It can damage the tank or parts internal to the tank. Disconnect the vent hoses and make sure they aren't blocked going back into the tank and filler neck. You can remove the canister later but get the vent open first.

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Google "canisterectomy." That should fix it. Until you do, I'd be breaking that seal every 50 miles or so to make sure you don't suck in the sides of your tank.

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Thanks every one. I figured a little pressure relief could be normal, just like when you open the car gas cap when it's real low but suction didn't seem normal to me. I see three hoses going into the canister. Does anyone know off hand which one(s) is for the tank vent and do I need to lift the tank in order to access the hoses in an R? Thanks for all your input. For me, one of the joys of owning a new bike is all the learning that goes with the experience.

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Morning kalali

 

The canister is usually marked BUT that tells you nothing as the hoses could be on the wrong nipples.

 

Easy way-- just open the fuel filler cap then blow into the hoses. Air (or hiss) coming out of the open fuel filler cap tells you that one is tank vent,, air coming out of hose behind R/H foot peg tells you that one is the atmospheric vent line,, the one you can't blow through is the one going to the purge valve on L/H side of bike.

 

When you connect the tank vent hose to the atmospheric vent line BE SURE to cut the bottom of the vent line (the one that comes out behind the R/H foot peg) to have a 45° angle on the bottom so the venting fuel tank doesn't suck road water into the fuel tank.

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+1

Vacuum is an incredible power.

 

Morning Andy

 

Actually vacuum has limited power & for most purposes can't even reach true max (per altitude & atmospheric pressure).

 

It isn't the vacuum itself that does the damage it is the atmospheric pressure pushing on the other side that does the damage.

 

 

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Afternoon Michaelr11

 

Unfortunately that link talks of removing the fairings. That is a LOT of extra work to simply remove the Evap Can.

 

The Evap Can be removed & the system plugged off without removing the fairings if the hose from the evap control valve is simply plugged off-- at either the L/H side evap control valve, or even simply plugging the 3rd hose at rear of bike.

 

The valve removal & plugging the TB nipples can then be done at a much later time (if even desired) when the fairings are removed for another service.

 

 

 

 

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+1

Vacuum is an incredible power.

 

Morning Andy

 

Actually vacuum has limited power & for most purposes can't even reach true max (per altitude & atmospheric pressure).

 

It isn't the vacuum itself that does the damage it is the atmospheric pressure pushing on the other side that does the damage.

 

True. Max pressure differential you will get at the coast is around 14.7 psi (101 kPa) - slight variance depending on atmospheric conditions. Even less at altitude (12 psi, 83 kPa here in Denver). And, you'd be hard pressed to pull a perfect vacuum in a plastic tank filled with a volatile liquid.

 

It's the surface area of the tank (considerable) that contributes to the large potential for deflection, even with small pressure differentials.

 

Irregardless of the physics, everyone is correct, in that it can do some painful damage to components inside the tank. In this instance I'd call it "powerful".

 

Whatever your remedy, don't dally.

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Well, went ahead and removed the canister. Literally a 15 minute job including zip tieing the vent hoses neatly by the R/H foot peg. As mentioned, the hoses are marked at the canister; E, A, and FT. I wanted to make sure the process is reversible by not cutting anything and labeled the hoses and plugged the E hose going to the evap solenoid. The parts removed included the canister and the canister vent hose. I now have two vent hoses; one from inside the gas tank and another from the tank overflow area - hole on the inside lip of the fill area. Just to be sure I didn't break anything, took the bike out for a quick ride and it ran just like it did before with no issues. One thing I know for sure is that I'll no longer have a suction when opening the gas cap and that was the ultimate purpose of this mod. Thanks to all the folks who take the time to make all this information available to newbies like me and educating a new generation who can pass it all on to the next.

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Just one other note: I had the same problem and when I disconnectd the vent line from the canister it dripped fuel.

Result: The vent line had a split in it inside the tank and caused the fuel leak. So if it starts to leak, you will need to go into the tank and replace the line.

Another 2 cents: The 2 small lines coming out of the tank, One is for venting and the other is for overfill/water drain from the cap area, (You can see the small hole at the top of the cap assy. when the cap is open).

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I now have two vent hoses; one from inside the gas tank and another from the tank overflow area - hole on the inside lip of the fill area. One thing I know for sure is that I'll no longer have a suction when opening the gas cap and that was the ultimate purpose of this mod.

 

Morning kalali

 

You can still get a suction when opening the gas cap so don't totally disregard that happening. IF the vent hose plugs with mud or gets pinched during service the vent can plug & cause a suction.

 

Make sure you cut the bottom of the VENT hose at a 45° angle as it can now suck road water in. Remember as the fuel tank level lowers due to fuel usage that fuel used MUST be replaced with outside make-up air. That make-up air can only get in through that vent hose so as the fuel is used & is replaced with air that (make-up) air can also bring in road water. With a straight end hose the road water can drip down the vent hose then form a droplet on the square end & get sucked in.

(With an angled hose end those droplets won't form on the bottom).

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Make sure you cut the bottom of the VENT hose at a 45° angle

 

Thanks. I saw that tip from you in an older thread and keep that in mind. But I wanted to first try to fit a small filter at the end of that vent hose before making the 45 degree cut.

By the way on a separate note, how is crankcase ventilation handled in these oilhead boxer motors?

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thanks. I saw that tip from you in an older thread and keep that in mind. But I wanted to first try to fit a small filter at the end of that vent hose before making the 45 degree cut.

---That doesn't always work like expected as the old venting fuel vapors turn to varnish in the filter then mix with dust/dirt pulled in & plug the filter, then you are back to the venting vacuum issue (better off with an angle cut & open vent hose)

 

By the way on a separate note, how is crankcase ventilation handled in these oilhead boxer motors?

---The engine vents through a hose to the air box & a timed vent passage through the rear crankshaft main bearing area.
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The 45 degree cut implemented. And thanks again for the tip. On HD/Buell 1200cc motors its common practice to divert the breather hoses to the airbox into an external catch can to collect (and periodically empty) the mixture which turns into a creamy goo.

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The 45 degree cut implemented. And thanks again for the tip. On HD/Buell 1200cc motors its common practice to divert the breather hoses to the airbox into an external catch can to collect (and periodically empty) the mixture which turns into a creamy goo.

 

Afternoon Kalali

 

Ah, but your 1100 air box does have an oil/water/goo drain (see pix below).

 

There is a lower chamber in the air box that c-a-n retain some of the oil (blow by) from the breather hose. Doesn't hurt to drain it every once in a while.

 

AirBox-1.jpg

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Excellent. I'll take a closer look tomorrow but (in the meantime) that begs the question if there's a way to access this "drain" plug without having to remove the airbox? I'm sort of lucky since the "R" is very uncluttered when compared to the "RT" and most things seem to be readily accessible.

As a side note, I just went through my second tank of gas today (with good dose of Techron added) since I bought the bike two weeks ago and am truly enjoying the bike. My shifts are a lot smoother and am finally feeling at home on the saddle. Its also good to know there's a whole lot of folks out there who jump in and help out with all the growing pains .....

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