Easiest way to check that is to blow through the vent tube.
If it is a California model it will have a canister connected to the vent tube.
Disconnect it and route the tube to outside air.
Be careful when routing the tube because it is easy to pinch it closed under the seat.

 

Well I got home today and "sucked" on my gas cap and learned that it is venting properly. So what could be causing the running out of gas type stumbling??? I installed a high flow Pingel petcock last night but haven't had suitable weather to take the bike out and see if it makes a difference. I only know that several years ago I had the same problem with my Shovelhead and all was well once I installed a Pingel and got rid of the in line fuel filter. So, we'll see this weekend.

 

My vented gas cap is not a check valve, it eliminates vacuum and pressure as it's supposed to.
Here is something to consider if you haven't already, last year I put an inline glass fuel filter on my bike just to have more than just the tank screen. My bike will not run correctly with it. Didn't dig too deep to find out why but all is well without it. Not needed anyway.....

 

Oh yeah, inline filters definitely suck - especially the glass ones. Most inline filters are designed to be used with a fuel pump and when the gas in the tank of a normally aspirated bike gets down under half full there isn't always enough weight/pressure to flow gas through the filter and the carb bowl can get starved.

 

After changing out the petcock and testing the gas cap vent I rode the bike to work this morning without so much as a hiccup. Hopefully I can get a bunch of miles on it this weekend and see what happens.

The worse part about buying a used bike is the first few weeks it takes to get it all unf*#&!d.

 

If it boggs down again, just crack the cap loose and see if it recovers.

 

Bingo!

No need to get homoerotic with your gas cap.

 

Wouldn't that me motoerotic?????

 

I fixed a Softtail this week that had a bad gas gap, it would idle but stuttered and died when you tried to ride it....undid the gas cap and it was fine, fitted a new one and it's still fine...**** happens...even to Evo's Lol!

 

I'm not that but I am a gasaholic, a chromosexual and a choppaphile.

I think the new petcock fixed the problem. It hasn't happened again.