Sorry for the confusion. The cap was originally vented. Because I had this odor problem I had a guy install the carbon filter. This filter set up needs to be re-designed. They connected the solenoid to the brake wire that opens the vacuum line from the carb to draw out the vapors. I now have a non-vented cap (plugged with some rubber) with a canister and a vacuum line to the carb. The vapor line comes off the tank neck to the canister. Any ideas how this could work?