aftermarket gas cap and venting?

[bschur13]

I put an aftermarket (on the cheap side) gas cap on my bike and I noticed that it is obviously not breathing properly.  I did notice that prior to replacing the cap that the stocker has a fancy valve system that allows pressure to escape when it builds up.   

After about an hour of riding today the pressure was built up to the point that I could hear it (after engine is off) squeezing out of the cap and when I do open it fumes rush out and a little bit of gas that is caught in the cap leaks out.   

Is it a major issue that can mess up my fuel system or should I just keep the cap on loosely or open it up occasionally when on a ride? 

 

[DucHead]

An aftermarket cap should not prevent the tank pressure from equilibrating.

It sounds like your vent hose is kinked or clogged.

I believe all Monsters have the vent hose in the same location: right side, rear part of the tank, there is a hose that drops down and exits somewhere near the right foot peg/rearset and acts as the tank vent.  Make sure that the hose is not kinked or obstructed.

[corey]

it seems like they have a habit of getting kinked when you put the tank back down without really paying attention and making sure you pull the vent hose into the proper spot.

[ducpainter]

I don't think the vent tube comes in to play with his cap.

The vent tube doesn't come in to play if you remove the little rubber extension from the cap 'bung' either.

[bschur13]

I don't think the vent tube comes in to play with his cap.

The vent tube doesn't come in to play if you remove the little rubber extension from the cap 'bung' either.

if its not the vent tube then how does this affect the pressure then?  I guess I am looking for clarification on the above statement.

also I put my bike in a storage unit so Ill get there later this week to check the tube coming off the tank. 

[corey]

to clarify: there's a little rubber nipple right inside your cap. i was having venting problems on my tank (turns out after some mods this winter, i found it to be a crimped off vent hose), and i could hear a whistle coming from the fuel cap. I would open it, and WOOSH... rush of vapors from the pressure equalizing. Removed that little black rubber nipple, never had the problem again.

[ICON]

I had the same problem from another gas cap I had. What I did and fixed the problem was I removed this tiny, tiny little hex screw that was under the tank cap. Not underneath the cap itself. I took it off and no more sounds, bubbles or pressure tyring to escape. Love it.

[bschur13]

I had the same problem from another gas cap I had. What I did and fixed the problem was I removed this tiny, tiny little hex screw that was under the tank cap. Not underneath the cap itself. I took it off and no more sounds, bubbles or pressure tyring to escape. Love it.

i noticed a little hex/set screw (well it looks like a set screw to me) under the cap when you screw it off to put the gas in the tank.  It looks like it is there for no reason. 

Does it sound like we are talking about the same screw?   

[ducpainter]

if its not the vent tube then how does this affect the pressure then?  I guess I am looking for clarification on the above statement.

also I put my bike in a storage unit so Ill get there later this week to check the tube coming off the tank. 

The vent tube in the tank originally led to the emissions canister. The rubber extension under the cap allowed the fuel vapors to travel from the tank to the tube via the cap vent.

If you aren't using a stock cap there is no connection to the rubber extension so the tube has nothing to do with it.

[ICON]

i noticed a little hex/set screw (well it looks like a set screw to me) under the cap when you screw it off to put the gas in the tank.  It looks like it is there for no reason. 

Does it sound like we are talking about the same screw?   

Yup, that is it. Now, I am only telling you what I did. The good thing about that little screw is, you can always put it back. But yes, I took mine off and it has been fine since.