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Old 03-03-2017, 04:21 PM   #81
jeffsaline
 
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Default Re: Fuel Cap Vent and Lock Cylinder

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Originally Posted by Adambomb946 View Post
So whats the best method in creating or finding a new gasket underneath the bottom most valve. Mine is completely dissolved into a black goo.
I'd probably make one using gasket paper and a sharp pencil and razor blade. Maybe a drill bit to punch a small hole as needed.

You should be able to get gasket paper at a local auto parts store. If you have a relationship with a mechanic you might be able to score a small piece for free.

Best,

Jeff
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Old 03-03-2017, 08:56 PM   #82
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Default Re: Fuel Cap Vent and Lock Cylinder

Thanks for the idea Jeff. I ended up carefully cutting a peice of old inner tube to match the gasket as closely as I could. Put everything back together with the "new" gasket installed and everything seems to be working fine. One question, how much resistance is there suppose to be when blowing into the nipple? Should it be easy like blowing through a straw or like blowing through a straw thats slightly clogged?
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Old 03-03-2017, 10:44 PM   #83
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Default Re: Fuel Cap Vent and Lock Cylinder

Quote:
Originally Posted by Adambomb946 View Post
Thanks for the idea Jeff. I ended up carefully cutting a peice of old inner tube to match the gasket as closely as I could. Put everything back together with the "new" gasket installed and everything seems to be working fine. One question, how much resistance is there suppose to be when blowing into the nipple? Should it be easy like blowing through a straw or like blowing through a straw thats slightly clogged?
My experience with inner tube material in today's fuels is it won't last. I've had reports of only two weeks. Hope you have better luck than I forecast. I've even had issues with Buna-N Nitrile in contact with fuel. It tends to sometimes swell and degrade.

I don't know about resistance and blowing into the nipple. I just make sure the passages are clear and the valves function.

Best,

Jeff
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Old 03-04-2017, 09:00 PM   #84
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Default Re: Fuel Cap Vent and Lock Cylinder

That never crossed my mind as far as the rubber degrading but its enough to make me worry. I'll do some searching for gasket paper as soon as i can find a suitable size. What thickness do you reckon the gasket is or closelt matches? 1/32 or 1/64? Thanks again
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Old 03-05-2017, 05:01 PM   #85
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Default Re: Fuel Cap Vent and Lock Cylinder

Quote:
Originally Posted by Adambomb946 View Post
That never crossed my mind as far as the rubber degrading but its enough to make me worry. I'll do some searching for gasket paper as soon as i can find a suitable size. What thickness do you reckon the gasket is or closelt matches? 1/32 or 1/64? Thanks again
I haven't had one open in a while but I think 1/32" or 1/16" gasket paper would work fine.

Best,

Jeff
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Old 08-20-2017, 12:55 AM   #86
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Default Re: Fuel Cap Vent and Lock Cylinder

One of the most useful maintenance threads on the board!

Non-Calif... I cleaned the cap venting system as described but later on a trip, (of course), ran into venting problems that left me dead on side of freeway just outside Phoenix till the cap was opened. Later at camp it was found that the tank vent line (inside the tank) from back by the seat up to the gas cap, was blocked. Easy to test for, just use tubing to blow air through the vent line while the gas cap is open, in my case no air would pass AT ALL. It should let a little air pass so the engine isn't starved of gas by vacuum in the tank.

Ran a cable up the tank vent tube from back by the seat and hit something a bit more than a foot up inside the vent line. What came out (with some considerable effort) looked like a rotted ball of rubber that had turned to a sticky goo mess. My best guess is that this was a restrictor that would let air pass via a small hole, but restrict gas flow out of this line should you invert the bike so you don't get a puddle then fire. So.. with gas cap open blow air up the vent line, it should pass air. Age and/or Ethanol are the suspected causes of breakdown of this restrictor.

Have never heard mention of a restrictor in that vent line, so perhaps this was some aftermarket mod by the PO. Doesn't matter... easy to test for. Also had the symptom of gas cap always whining even after all the above gas cap vent service was accomplished months earlier.
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Old 08-20-2017, 01:41 AM   #87
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Default Re: Fuel Cap Vent and Lock Cylinder

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Originally Posted by WiRider View Post
One of the most useful maintenance threads on the board!

Non-Calif... I cleaned the cap venting system as described but later on a trip, (of course), ran into venting problems that left me dead on side of freeway just outside Phoenix till the cap was opened. Later at camp it was found that the tank vent line (inside the tank) from back by the seat up to the gas cap, was blocked. Easy to test for, just use tubing to blow air through the vent line while the gas cap is open, in my case no air would pass AT ALL. It should let a little air pass so the engine isn't starved of gas by vacuum in the tank.
I've been mucking around with my tank vent also, to the point of removing all of that nonsense in the cap and putting one of those check valves at the end of the tube. Dumbass me never thought to check the tank tube. Just ran outside at 11 at night and squirted some wd40 down the tube.... I could hear it fill. I put 2 feet of clear hose at the bottom of the tube, bringing the other end up towards the bars so it didn't piss all over the place. I ran a wire down the tube and then had my collection of wd40 appear at the bottom. I took my fork oil syringe filled with more wd40 and filled it til the external tubing came up to the height of the gas cap end. It's gonna soak overnight so I can drain it and give a blast of air down the tube in the morning. Thanks for giving me that obvious, but overlooked suggestion.

Where were u stranded outside PHX? Interstate 17? Not much going on once u pass Anthem. Glad u got it resolved.
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Old 08-21-2017, 11:44 PM   #88
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Default Re: Fuel Cap Vent and Lock Cylinder

Southbound on 17 went dead and left me sitting at Google Earth Lat 34° 43.728'N Long 111° 42.517'W. Downhill fast altitude loss for a long time so air pressure rising but tank not getting vented and went to a negative pressure so just stopped feeding gas to the carb. Thought it was fuel petcock problem or vacuum line to petcock collapsing. Would not start. After some while tried opening gas cap and heard big rush of air, bike started fine then. Rode with cap open till could work on it later, and then found that ball of black goo plugging the vent line a foot or so up inside the tank vent line as stated. Symptom of no air would pass through that tank vent line with gas cap open.

Months before trip had done this thread's gas cap service, but gas cap still whined. Gas cap still whines to this day. May repeat the gas cap service but am thinking part I need is mentioned as no longer available... so may be looking for old gas cap.

When broke down that spot... there was a trucker that went whizzing past and half locked his brakes, pulled over. Walked half a mile back to me to ask if needed help. Had just solved it... thanked him. Sure nice folk out that way!
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Old 08-22-2017, 03:06 AM   #89
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Default Re: Fuel Cap Vent and Lock Cylinder

Yup... no man's land! You were just east of Sedona.... probably 5000 ft. Beautiful area, but I wouldn't want to be stranded up there.
The ball of rubber might have been the seal that WAS just under the gas cap lid, where it ties in to the tank tube... at least I think there was a seal there. I added a 5/16" od o-ring there to ensure there's a seal.
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Old 10-10-2017, 05:21 PM   #90
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Default Re: Fuel Cap Vent and Lock Cylinder

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Yup... no man's land! You were just east of Sedona.... probably 5000 ft. Beautiful area, but I wouldn't want to be stranded up there.
The ball of rubber might have been the seal that WAS just under the gas cap lid, where it ties in to the tank tube... at least I think there was a seal there. I added a 5/16" od o-ring there to ensure there's a seal.
You are right! There is supposed to be an o-ring per 2002 Tank Drawing, 92055A and for Calif it's 92093. It's missing. Where it was sitting there's a thin layer of black crud all around. Ethanol got it drunk, swelled, and sticky. It was picked up by the tank cap when opened then got pushed into the vent tube when closed. Then in vent line it continued to break down and swell into goo and block the vent line. The vent port on the cap is a tapered piece that seals metal to metal when it fits right into the end of the metal vent tube, the 0-ring seems to be more to prevent rattling than a seal.

Down the vent line, it continued to swell as a ball of goo and plugged it up, sealed the tank air tight. Dropping in altitude fast on Hwy 17 for a long time the outside air pressure went up as tank pressure stayed the same, making inside the tank a bit of vacuum till overcame gravity and no longer could get gas to the carb.

Proof is going downhill long long ways engine starved of fuel and stranded me. Opening gas cap suddenly fixed the problem but had to leave cap open.

To check for this look for the o-ring and if still there you're ok. Not there then run a wire up the vent tube from back of tank to push it out. Stiff wire will go all the way through and come out at cap without much of a problem. I used a cheap household extension cord, one side, stranded wire. Most anything will work it's a big tube.

You already said your o-ring was missing... good chance is inside vent line, and good chance it's plugging vent line giving you problems. Engine fuel starved when going from high altitude to low? Popping cap open solve it temporarily?

Others may see this as well. Check for that o-ring!

Looking through whole thread others report fuel starvation, and indeed is caused by cap in many cases. Before all that work run a wire up the vent tube... save ya lotta time and effort if lucky!
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Last edited by WiRider; 10-10-2017 at 05:53 PM.
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