[Dave K]

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This is a first for me and I have had this '81 since '81. It had been a tough Spring and I just now got the bike out. She is kept covered in my heated/air conditioned garage. Put a new battery in her and she fired right up. Went for about 5 miles, stopped to talk to a guy and she wouldn't start. This is a first! I could smell old gas, but I was back at the guys garage, where he has old outboard motors, lawn mowers and tractors, so I thought nothing of it. I pulled all the plugs and they looked to be in good condition and strong spark. I kept looking and couldn't find a thing, so after about 45 min., I tried to start her and she was reluctant, but she finally cleared out and ran fine. I then went for a 30 mile ride and parked her back in the mentioned garage at home again, but I didn't cover her. Went back out an hr. later and the smell of gas was strong and there was gas dipping from her carbs and onto the floor. I kneeled down to see what the heck was going on and I could hear what sounded like fuel boiling in her tank. I popped the gas cap and the boiling sound stopped along with the dripping of gas from the carbs. Now I have the gas all cleaned up and the a large fan clearing out the fumes in the garage. The thing I need to know is WHAT IS GOING ON! All these years and this is a first. There is around 34500 miles on the bike. The gas has last Falls gas in the tank with about 2 gal. of Av Gas LL 100 in her for the winter. Does the bike have a problem, or is it the heat and the gas? It is around 95º sunny and humid.

 

[agnogel]

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Hi Dave i am not up to speed on the 1100 but is there a vent pipe in the gas cap or the tank thats blocked

 

[peterbilt]

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the vent is built into the cap its probably plugged up cap you can either buy a new one or drill a hole in the cap itself very small hole will do

 

[Dave K]

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No, it is a sealed system, I think. You could always hear the gas vapors go hiss when you would take off the gas cap. Thanks for responding!

 

[Dave K]

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Peterbilt, I wasn't aware that the cap was vented! As from day one, it would hiss when removing the cap. Hmmmmm... I will look close at that cap and see where the vent hole is and make sure it is open. I am sure that would cause the leaking of the carbs.

 

[THEBIGRED1]

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Best to burn off all that old fuel and stay a bit close to home in the process. If you should encounter this again simply unscrew fuel cap and look for improvement. Are you using the fuel shutoff after you park the bike?

RED

 

[Dave K]

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I am NOW~! Never did before though.

 

[THEBIGRED1]

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I never did either until after I read a few threads on why fellows do. If something should go wrong and the petcock is off.....your much better off.

RED

 

[THEBIGRED1]

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Stant#10810........gas cap that has been discontinued. I believe I got mine from car quest.


RED

 

[TrikerBo]

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THEBIGRED1 wrote:

Stant#10810........gas cap that has been discontinued. I believe I got mine from car quest.


RED

I got a new gas cap from a dealership last year, has it recently been discontinued. Payed silly money

 

[THEBIGRED1]

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I paid 3.00 American.......and was instructed that my cap was no longer available at the time by the forum......as well as given the number mentioned. Nice bike friend.

RED

 

[notodd]

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are we suppose to hiss or not????????:?

 

[THEBIGRED1]

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Yes.

RED

 

[Ken Bergen]

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notodd wrote:

are we suppose to hiss or not????????:?

Yes they all do it.
As I understand it the cap lets air in very easily but it takes a couple of pounds of pressure to vent vapours. I would think it's a safety feature to help prevent spilling fuel when your bike takes a nap.:shock:

 

[glhonda]

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Ever see an unvented gas can expand to the size of a basketball in the mid day heat, only to collapse to the size of your wallet when the sun goes down?

 

[gido]

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Gas cap is supposed to be a one-way vent. Anti-pollution, safety, and all that jazz. Could the problem be the high octane AV gas?

I had a similar problem with my 750auto. Engine ran a lot hotter than a regular 750 and when the gas tank neared about one quarter full on a hot summer day (which would be 75 around here) it really affected the engine operation. As soon as I filled it up the problems disappeared.

 

[DaveO430]

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The AV gas may have a higher vapor pressure than auto fuel, not sure. Gasoline in the US was reformulated in the 80s to have a lower vapor pressure because of problems it was causing with the early fuel injection systems but AV gas may not have been effected by the change. Still your cap should have vented the pressure before it became too much for the float valves to retain. And get in the habit of shutting off the fuel when stopped.

 

[peterbilt]

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your going to have SOME fuel tank pressure but normally if you hear a whoosh when taking the cap off thats perfectly normal

now if the cap dosent vent you build up too much pressure and it actually pushes fuel into the carbs causing a leak those seals on the carbs cant handle alot of pressure i think the fuel pump on the 1100's only do a couple pounds of pressure just enuf to feed fuel to the carbs

i would run the bike with the cap off completely for awhile and see if the problem goes away hopefully it didnt blow out the seals on the carbs.

 

[Dave K]

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After my last post, I ran to the workshop to ponder. I took the gas cap and looked how it is made. There is a check like valve on pressure, where the cross bar(?) is located. This is spring loaded and if all is clean and all ports on the cap are open this should vent the system. I did all I can, to clean, check the spring for tension and make sure that the 4 vents on the underside of the very top part of the cap are open. I then checked the 2 ports on the bottom of the cap and it is these 2 ports, that push on the cross bar and it's spring, to vent the excess pressure out the ends of the cross bar and up through and out the 4 vent in the top of the cap. I used air pressure after the cleaning to see that this check valve system would open and of course close at a reasonable pressure.

Next, I was concerned about the boiling gas and what it may have done while the carbs were being cooked. Good thing I thought about it! I pulled the plugs, turned to "off" the kill switch and spun the motor. It appeared as if each piston was swimming in about a cup of gas. I have cleared the cylinders now and the oil is being drained, just in case it contaminated the crankcase.

I would say the Wing and I had a lucky day! Thanks for all the thoughts, ideas and especially the responses!

 

[THEBIGRED1]

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Nice catch. There will most definitely be fuel in the oil. Looks like you have done a motor flush without knowing it. Any remnants should evaporate after oil change. Good thing you did not run the bike. I believe I have read about fuel hydro-lock that resulted in engine damage.

Best to sort this out......and keep that petcock off while she sleeps.

RED