fuel cap issue

[Victor]

Hi folks, I recently finished a Wombat 125 with my daughter. Bike running well yet each time we take it for a ride the fuel cap fills with fuel and leaks out through the breather hole in the cap. I have to take the cap off and literally drain the cap of fuel. I've never seen such a thing. Anyone have any suggestions on how to resolve? All thoughts much appreciated.

[Thunderdogdownunder]

Does it have the black rubber gasket which sits on the inside of the fuel cap ..

[Bullfrog]

Is the vent/drain hole in the rubber gasket plugged?
Ed

[matt glascock]

Yep. If you're missing the gasket the cap will leak like a sieve. Also, if the gasket is present, make sure it isn't roached or dry-rotted. If that's all good, does the bike vibrate like crazy? That could be anything from loose motor mount bolts to an out-of-balance fly wheel, to an issue with the crank, to shot bearings, to...on and on and on. I have a M94 Wombat set up for MX and didn't particularly like fuel leaking out of the vent hole. I simply sealed the hole with epoxy, tapped in a 1/4" brass tube (you have to cut a corresponding hole in the rubber gasket so the tube can extend through the gasket, and then attached and ran a 16" length of 1/4" fuel line behind the starter number plate. Problem solved. I do see from time to time a bit of fuel entering the vent line but the height over the bars seems to prevent any drainage out of the tube - not any that I've noticed anyway.

[Bill2001]

The replacement fuel cap gaskets (still available from SH) have a dome on the bottom to mske a little "breather chamber". There is suppose to be a small, 1/32-1/16" , hole in the bottom of the dome for breathing and to allow drainback of sloshed fuel. Sometimes during the molding process that bottom hole gets plugged. There is also a vent hole in the top of the cap. Make sure both those vent holes are in fine fettle.

On the vent hose fitting: DuBro, inc makes R/C aircraft parts. They have barbed fuel cap fittings. The fitting that threads onto a #10-24 tapped hole is sized to fit a 5/32" hose. The hobby shop that stocks these fittings will also have 5/32" Silicone rubber or Urethane fuel hose that can be used for vent line. That setup.will make you the envy of your riding buds.

[matt glascock]

Ooh - that does sound slicker than my DIY job. I will look into those.

[Victor]

Thanks for all the comments. The cap is a new replacement and as you called it the vent in the bottom of the dome on the gasket was almost closed on the back side of the gasket. Opened that hole up, will let you know how it goes but seems like that was the issue.

[Bill2001]

When the gasket is molded, there is a little tit in the bottpm of the dome that is supposed form the.drain hole. The liquid rubber is forced into the mold and flows over the tit, making a flap.over the hole after the rubber cures. Over the years I've gotten almost neurotic about double-checking replacement parts.

Glad it works.

[Victor]

Went for a ride yesterday, much better day when you get home and all the fuel is in the tank instead of dripping all over the outside! Thanks again