Leaky gas cap

silverbear · Jul 14, 2009

I have had two chinese two strokes and put together a third for a friend. Every one of the gas caps leak. At one time I found a Honda 50cc cap that fit which did not leak... that one is long gone and another story. Someone here has figured out a simple fix to this problem, I hope. I like to keep the bike clean from oil and grease as much as I can and the leaky tanks are annoying. I never have more than a half a tank of gas, but it still leaks. Both of my bikes are step through frames so I have the tanks mounted behind the seat and they are not tear drop, but rectangular with a low profile. Any tips?
Silverbear

Retmachinist · Jul 14, 2009

silverbear said:
I have had two chinese two strokes and put together a third for a friend. Every one of the gas caps leak. At one time I found a Honda 50cc cap that fit which did not leak... that one is long gone and another story. Someone here has figured out a simple fix to this problem, I hope. I like to keep the bike clean from oil and grease as much as I can and the leaky tanks are annoying. I never have more than a half a tank of gas, but it still leaks. Both of my bikes are step through frames so I have the tanks mounted behind the seat and they are not tear drop, but rectangular with a low profile. Any tips?
Silverbear

Don't know what kind of tanks you are talking about? Rectangular, low profile? Are they the stock kit tank and cap?

John

silverbear · Jul 14, 2009

I bought these tanks from That's Dax as an alternative to the tear drop tanks. They use the same caps. Also the bike I put together for a friend had a tear drop tank with the same cheap cap. I suspect it is the same cap as on many of the chinese engines. It is the cap which is leaking and doesn't really matter which style tank is used. I was hoping that a different gasket or an O ring or something would solve the problem of leaking in the stock caps. Others must also experience this or is it just me? One difference in tank shape is that the rectangular one which fits behind the seat is a lower profile so that the fuel is closer to the cap. But if the cap seals the gas in then it shouldn't matter. As I said in the prior post, I once had a cap from an old Honda moped which fit the stock chinese tanks and it did not leak at all. Thanks,
Silverbear

bodydropped · Jul 15, 2009

mine leaks also on both my bikes since the first day i installed the kits, i would like to know to. is there is another option or a quick fix?

camlifter · Jul 15, 2009

it's not the gasket that leaks, it's the air vent. when you fill it close to full or even if you only fill it half way, leaning the bike over of riding over rough ground gas splash's up into the holes for the air vent and leaks out. if you look at the cap you will see a hole outside of the gasket area, thats where the gas is coming from. i've been planing to seal that hole up with jb weld and drilling a hole in the top of the cap and running a vent hose off it like on dirt bikes. haven't tried it yet though. if anyone knows of better cap i'd like to try it. sucks getting gas on your nice new paint.

silverbear · Jul 15, 2009

I'm not familiar with dirt bike caps and the vent hose. Describe it. Is it just a few inches long so that rain doesn't come in... and then hangs over the side? That should be simple enough. As you say, a little dab of JB weld would seal up the existing vent hole and then drill a hole in the top of the cap for a small diameter hose... either with a threaded nipple or just stuck in the hole and dabbed with another bit of JB weld. Should work, but I'll wait to see other posts. Maybe somebody sells a real cap that works as it should. Wish there was a source for those old Honda moped caps. Fit tight, looked good and didn't leak at all.
Silverbear

Bikeguy Joe · Jul 15, 2009

I just drill a hole in the middle of the cap (1/16") and it vents through that. I only get a little 'leak' when it's all the way full, hot day, bumpy riding. (which is not very often)

Cabinfever1977 · Jul 15, 2009

i replaced my cap with a rubber/plastic oil plug type of cap from napa.
and i drilled a hole in the center of cap with a very small dia pipe for venting.
napa part:$3 oil filler cap, part #703-2300

$1.79 from napa online:
Oil Filler Cap - Retail

Ghost0 · Jul 15, 2009

We sell gas cap gaskets but as was mentioned the gasket is only part of the problem. Adding the gasket does cut down on the leaking a tremendous amount but there is still the vent that can leak. Some of the alternate venting methods mentioned should work.

Dave31 · Dec 20, 2009

I have this cap that leaked real bad, I drilled 8 holes to get the thing to stop leaking.

I first drilled two holes underneath the gasket, that did nothing. Then I drilled two more under the gasket...kinda helped.

So then I drilled two holes on the neck of the cap, that really helped but still would leak when I shake the tank a little. So I drilled two more a little lower on the neck and that stopped all the leaking

With the tank removed off the bike I can flip it upside down/upright and shake it like there is no tomorrow and not one drop of fuel.

AaronF · Apr 2, 2010

fairracing31 said:
I have this cap that leaked real bad, I drilled 8 holes to get the thing to stop leaking.

I first drilled two holes underneath the gasket, that did nothing. Then I drilled two more under the gasket...kinda helped.

So then I drilled two holes on the neck of the cap, that really helped but still would leak when I shake the tank a little. So I drilled two more a little lower on the neck and that stopped all the leaking

With the tank removed off the bike I can flip it upside down/upright and shake it like there is no tomorrow and not one drop of fuel.

I think I'll give your method a go tomorrow.I'm tired of gas/oil all over the darn place! Thanks Fair.

Dave31 · Apr 2, 2010

There are two different types of caps that come with the kits (That I know of). The one pictured in my previous post has this rubber or plastic stuff inside which really keeps the fuel from trickling out and the fuel will come out from the cap cover. By drilling the holes it allows the fuel to drain out before it starts to spill out of the cover.

The chrome part of the cap is just a cover, and in my experience thats where the fuel always comes out of.

The other style of cap does not have that rubber or plastic and does not leak as bad in my opinion.

The biggest problem is that the cap does not seal with the rest of the part of the gas cap, but I guess if you seal it it would not vent as well. Drilling the holes seems to work for me, may not work for everyone.

Photo 1 shows the two style of caps. On left is the one with a rubber or plastic inside with the spring. The one on the right is without it.

Photos 2 & 3 show the cover off a cap with out the plastic.

GoFastBicycles · Apr 4, 2010

You come up with some of the best help (solutions) I personally want to thank you for your passion and willing to help.

Thank You,

Adam

Dave31 · Apr 4, 2010

GoFastBicycles said:
You come up with some of the best help (solutions) I personally want to thank you for your passion and willing to help.

Thank You,

Adam

Thank You Adam, that is very much appreciated. And Thank You for being a member of Motorbicycling.com and all you share with us. It takes great members to make a great forum.

psprat496 · Apr 4, 2010

Bikeguy Joe said:
I just drill a hole in the middle of the cap (1/16") and it vents through that. I only get a little 'leak' when it's all the way full, hot day, bumpy riding. (which is not very often)

So if I fill the current vents with some jb weld and do what your saying about drilling a new vent hole straight through it should work? There is enough air that flows in?

AaronF · Apr 5, 2010

fairracing31 said:
There are two different types of caps that come with the kits (That I know of). The one pictured in my previous post has this rubber or plastic stuff inside which really keeps the fuel from trickling out and the fuel will come out from the cap cover. By drilling the holes it allows the fuel to drain out before it starts to spill out of the cover.

The chrome part of the cap is just a cover, and in my experience thats where the fuel always comes out of.

The other style of cap does not have that rubber or plastic and does not leak as bad in my opinion.

The biggest problem is that the cap does not seal with the rest of the part of the gas cap, but I guess if you seal it it would not vent as well. Drilling the holes seems to work for me, may not work for everyone.

Photo 1 shows the two style of caps. On left is the one with a rubber or plastic inside with the spring. The one on the right is without it.

Photos 2 & 3 show the cover off a cap with out the plastic.

Great information as always Fair

I haven't had a chance to try your mod yet,I'll post the results here soon! Thank you man.

Search

Leaky gas cap

silverbear

The Boy Who Never Grew Up

Retmachinist

New Member

silverbear

The Boy Who Never Grew Up

bodydropped

New Member

camlifter

Active Member

silverbear

The Boy Who Never Grew Up

Bikeguy Joe

Godfather of Motorized Bicycles

Cabinfever1977

New Member

Attachments

Ghost0

New Member

Dave31

Active Member

Attachments

AaronF

New Member

Dave31

Active Member

Attachments

GoFastBicycles

New Member

Dave31

Active Member

psprat496

New Member

AaronF

New Member