Gas Tank Pressure??

[haze324]

The day I picked up my bike I road it home about 200 miles and as I was getting home it died. As I got a little anxious I checked to see if I had gas and noticed a bunch of air pressure was released when I popped off the gas cap. I later found out this happens.

Well today I've been fumbling around with my new pipes, jets, carb, etc. and after I thought I had it tuned I rode for about 20 minutes filled up the tank wtih gas and was gonna go check out how it was running. It road for about 10 more minutes before it started sneezing, like it was about to run out of gas. I pulled over. Not sure what it was...at first I thought I hadn't adjusted my carb properly, then I had an issue with gas filter earlier in the day, that wasn't it. Then sure enough I took the cap off, a ton of pressure was released and the dog fired right up and started hauling ass again. It started sneezing again 10 minutes later and then I just went home.

What causes this? Why now after I changed my pipes? And whats the fix?

Thanks guys.

 

[Raywood]

I'm sure you meant vacuum and not pressure. You have a plugged vent in your right gas cap. Well documented on here. Remove the cap and take it apart and clean it with carb cleaner. It gets gummed up after a while and freezes up the check valve.

Later,
Ray

 

[haze324]

I'm sure you meant vacuum and not pressure. You have a plugged vent in your right gas cap. Well documented on here. Remove the cap and take it apart and clean it with carb cleaner. It gets gummed up after a while and freezes up the check valve.

Later,
Ray

Thanks man. Yeah I did a search for pressure instead of vacum that would make alot more sense. Ok, i'll clean it out tomorrow!!

I was running lean and changed out my jets today. Does running lean/heat cause for a vacuum/pressure build up in the tank?? I read something along those lines in another post, but it wasn't too clear.

 

[Gas Man]

Yeah get that straighten out first before you continue screwing with the jetting.

 

[ezrstl]

Gas cap breather valve

I would recommend removing the white valve in the bottom of any Big Dog fuel cap. They unscrew out. They are a source of much frustration.

 

[Raywood]

I would recommend removing the white valve in the bottom of any Big Dog fuel cap. They unscrew out. They are a source of much frustration.

Welcome ezrst, post in the "Introduction" section and post a pic of you scoot. You may have the oldest Dog here!

Later,
Ray

 

[V]

Had the same prob. with my 05, removed the check valve on the right side gas cap solved the problem.


V

 

[haze324]

Had the same prob. with my 05, removed the check valve on the right side gas cap solved the problem.


V

I unscrewed it today and cleaned it all out pretty well.

Are you saying to unscrew the center portion and just leave the cap and rubber? If that works.....why does BD even put the check valve in there?

 

[Raywood]

I unscrewed it today and cleaned it all out pretty well.

Are you saying to unscrew the center portion and just leave the cap and rubber? If that works.....why does BD even put the check valve in there?

The check valve protects your paint if you should over fill.

 

[ezrstl]

The white check valve in the fuel cap is mostly EPA related. Big Dog does a pretty good job sealing the paint behind the tank saver, so paint lifting from gas/fumes is held to a minimum. With that being said, if you overfill your tank, fuel can come out of the breather passage when you put the bike on it's kickstand. Fill it full, but don't overfill and park it.

 

[Gas Man]

yes, remove the check vlv... I have never had one in mine... removed by the dealer as its not needed...

dis-essembled

 

[V]

I was told it was a EPA deal. Didn't put it back.


V