the reason your gas cap leaks...

[bairdco]

there is a small vent hole near the top of the gas cap, more or less hidden by the gasket (see photo.)

when your tank's full, the four holes on the bottom of the cap are submerged in gas, and that creates a siphoning effect, and causes the gas to leak out of the vent hole, all over your tank, your leg, your carpet, dog, etc.

if you plug it up with something, you're gonna seal the tank and cause vapor lock, so that won't work.

if you buy an aftermarket cap, like the chevy oil caps, make sure you open it up during rides to vent it, or again, vapor lock.

the best thing to do, is throw that tank in a fire and buy or make one that doesn't look like, well, a crappy china peanut tank.

i've got a pacer moped tank on the way. i'll let you know how that works....

 

[Venice Motor Bikes]

Or, you can only fill the tank 3/4 of the way... (Then it won't spill out)

 

[Cabinfever1977]

i only put a liter in my tank and i have a rubber oil cap. i drilled a hole in center of cap and stuck a thin metal line threw hole for venting.when i bring bike inside i can block off the vent.

 

[Mike Hunt]

i fill mine about halfway and i still get a little bit on the outside of the tank. doesn't really bother me.

 

[Kevlarr]

I don't think that's entirely right because mine leaks even if the tank's only 1/3 full.

I took a good look at the neck and I think that's where the problem lies. The area on the neck where the tabs from the cap go in isn't at all flat and there isn't much for the gasket to seal to, that and the fact that the rubber gasket is tapered to the outer edge so it's thinnest where it needs to seal the most. Also whenever I remove my cap the entire bottom of the gasket is wet but the top is relatively dry.

Even if the holes were below the level of the gas it wouldn't siphon because of the holes where the locking tab goes through.

 

[drhofferber]

I don't think that's entirely right because mine leaks even if the tank's only 1/3 full.

I took a good look at the neck and I think that's where the problem lies. The area on the neck where the tabs from the cap go in isn't at all flat and there isn't much for the gasket to seal to, that and the fact that the rubber gasket is tapered to the outer edge so it's thinnest where it needs to seal the most. Also whenever I remove my cap the entire bottom of the gasket is wet but the top is relatively dry.

Even if the holes were below the level of the gas it wouldn't siphon because of the holes where the locking tab goes through.

discountscooterparts.com has locking gas cap...17.00...heavy duty and dont leak and stops the varments at work from getting into the tank...ha...Dennis

 

[Srjeeper]

discountscooterparts.com has locking gas cap...17.00...heavy duty and dont leak and stops the varments at work from getting into the tank...ha...Dennis

Dennis, are all their gas caps the same size as those used on kit tanks? The B2 non locking cap looks like it should do the job providing it's the correct size. That one does not extend down into the tank yet it's still vented.

 

[drhofferber]

Dennis, are all their gas caps the same size as those used on kit tanks? The B2 non locking cap looks like it should do the job providing it's the correct size. That one does not extend down into the tank yet it's still vented.

the cap i use from them is item#169...i have them on all three bikes...for over a year...paint them black and they are a great addition to your bike...Dennis...oh to answer your...da...i would asume so...

 

[azbill]

their site says out of stock

 

[Srjeeper]

I just ordered one of they're B2 scooter caps (item 191) to see if that stops the leaking.

I'll post the results after I give it a try.......film at 11......

 

[Srjeeper]

I just ordered one of they're B2 scooter caps (item 191) to see if that stops the leaking.

I'll post the results after I give it a try.......film at 11......

UPDATE......

Got the cap yesterday and it fits perfectly. It's really tight to screw on but NO LEAKING!!!!

It's plain metal, so it'll need to be painted, but that's a small price to pay for a no more leaking cap.

No film at 11......

 

[ryanc2bill]

I took the gasket off, traced it with a pen onto a old bicycle inner tube and took siscors and cut two new gaskets, put them behind the original one and it works great!! It's takes a little pressure to put it on but the seepage is very minimal! And I don't have a problem with creating a vaccum in the tank! Full tank and I'm not getting gas everywhere!!

 

[2door]

I took the gasket off, traced it with a pen onto a old bicycle inner tube and took siscors and cut two new gaskets, put them behind the original one and it works great!! It's takes a little pressure to put it on but the seepage is very minimal! And I don't have a problem with creating a vaccum in the tank! Full tank and I'm not getting gas everywhere!!

The rubber that most innertubes are made from will swell and soften after extended exposure to gasoline. There are materials that will work with gas however but you need to assure it is compatibale with ethanol based fuels too.

Tom

 

[thunderchicken]

I solved my problem with my leaking gas cap. My cap is the cheap o kind the inner part is just pressed into the cap then peened on two sides to keep it in. It crinkled around the edges. That is where the gas is leaking from. Doesn't matter how good the gasket is it goes up and around and out the crinkles. I sealed the crinkles with epoxy the standard 5 minute. Web sight said it is solvent and fuel resistant. Anyways I sealed all but about 2 of the crinkles left a few for venting thus no vapor lock. Didn't completely stop the fuel but just a few dribbles is tolerable.

 

[bairdco]

i got a cap off an old moped after i made this thread. after 3 years or so, no leaks. not even when my bike (and me) bounced end over end down the street...