I got myself a new Honda Accord radiator cap. It holds pressure, but it's kind of on the bottom of the spec though. Better than what I had.
Cut one tab off and the cap fits fine.
Back to getting the airbox squared away. This hose is to the crankcase breather that goes back in the stock airbox.
Here's were it comes out of the crankcase.
Here's what you need for a new crankcase breather.
Chop down the stock hose out of the crank case breather.
Good to go.
I have now successfully swapped the hypercharger for the mooneyes air filter kit, re-jetted the carb properly, removed the already bypassed REED valve system, bypassed the carb warmer, and moved the crankcase breather. This is all basic stuff that should be done when doing an open airbox to a 1500 Vulcan.