I was wondering, my fuel tank is being pressurized when I ride, are these gas caps supposed to maintain a pressure, or is my vent plugged up?
Gas Cap question
- Thread starter bonth123
- Start date
Normal, as gasoline is quite volatile and the cap is there to contain these fumes. You may notice your bike "farts" occasionally when sitting hot in the garage. That's the excess pressure being vented from the cap.
Thanks, I don't hear a fart so much as a hissing sound. It also causes the garage to fill with fumes...may leave it outside until it cools so I don't have to smell the fumes. Of course, it was a little over 100F when I was riding, so that may add to the excessive pressure, black bike in high heat - the fuel was probably close to spontaneous combustion temp in the tank.
ToddC
Site Supporter
Is it still 100 degrees in E WA??? Riding over tomorrow. Where are you at Bonth123??
ToddC
ToddC
The Cheese
Sounds mostly normal to me.
If it's hard to turn apply some moly paste between the rubber seal and metal underside of the cap. Grease works too, seems to disappear faster than moly tho.
If it's hard to turn apply some moly paste between the rubber seal and metal underside of the cap. Grease works too, seems to disappear faster than moly tho.
No, it is only in the upper 80's today, which is much more comfortable for riding. I am in Moses Lake, PM me and I can give you my contact info...always looking for an excuse to put miles on, or go for a coffee in another county.
It opens easilly enough, just releases pressure like a fuel injected car.
Unlikely... it would have to be near 500?F for that to happen.
Ok, maybe I was a little facetious on that one
The tank, or false cover piece, was too hot to touch with bare skin...but I am sure it was far below 500F, doubt it passed the 250F mark
Ok, maybe I was a little facetious on that one
The tank, or false cover piece, was too hot to touch with bare skin...but I am sure it was far below 500F, doubt it passed the 250F mark
I know you were, just joking with you.
The vent in the cap will allow some pressurization, since it has a spring inside. To find out how much pressure, take the cap off, remove the small hose and suck or blow on / into the barb. You will feel the amount of pressure it takes to open the pressure relief valve.
John OoSTerhuis
Life Is Good!
The ST1100 fuel tank filler cap vents both ways, pressure and vacuum. I've got a schematic somewhere in my desktop's archive. Probably posted it here a few years ago...(?)
John
via iPhone 6
John
via iPhone 6
I saw somewhere that you can diassemble the cap and clean them up internally to get them working correctly, may try that after I get a backup cap. It works, but seems to be higher pressure than I am used to seeing in a carbureted bike.
John OoSTerhuis
Life Is Good!
Fuel filler cap schematic:
Disassembly document:
[Oooops, the Word file with pictures by Arnold Van Remoortere is too large for the forum rules. Email me for a copy.]
HTH, John
Disassembly document:
[Oooops, the Word file with pictures by Arnold Van Remoortere is too large for the forum rules. Email me for a copy.]
HTH, John
You might try spraying some carb cleaner into the small hose barb to clean out any gunk that might be affecting the operation. I think I'll do that to my cap just for S&G's.
EDIT : I sprayed the vent in my cap with the carb cleaner - no change. Doesn't take that much blowing or sucking into or out of the barb to get good flow.
EDIT : I sprayed the vent in my cap with the carb cleaner - no change. Doesn't take that much blowing or sucking into or out of the barb to get good flow.
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Well, I found the source of the fuel smell...I had a fuel line under the false tank that was not secured with a clamp of any type...so when the tank pressurized it would force some out at that connection. I also used a small probe to move the internal parts of the cap and voila, no more excess pressure, must have been stuck with gunk or something, but it works good now. I think this winter I will let is soak a little in some carb cleaner and see if that gets the gunk out.
Glad to see the tip about the moly paste... last fuel stop I had to get the multi tool out to turn the gas cap...whew... thought i'd never get it off!
Try some silicone grease ( dielectric grease ). Won't affect the seal material.
correct, grease will eventually deteriorate the seal. a silicone base grease will not interact with rubber
I haven't been inside my gas cap, but if there are rubber parts - gaskets - they will be damaged by carb cleaner. I want to take mine apart this winter to check it. I've managed to tip my bike over with a full gas tank and nothing leaks out (fortunately). Just wondering if this is normal, but cleaning it seems to be a good idea for preventative maintenance.
Btw, after reading about silicone grease in this or another thread recently, two days ago I squirted some powdered graphite/moly (for locks) in my gas cap lock (and, for good measure, all the other locks on the bike) and lubed the big gasket w/ a touch of silicone grease. Then I put the key in and out of each lock several times and turned each one. The gas cap opens sooooo much more easily now. Why didn't I do this sooner? It goes on my annual maintenance list.
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