Leaky gas cap

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

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

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?

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.

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

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)

__________________
If it ain't broke, and you mess with it long enough, it will be.

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

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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.

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