Motorcycle Repair: 1984 Honda vf700 magna wont rev above 2500 rpm, air passages, honda vf700

Question
I just bought the bike from a guy who said it had been sitting for over a year, and said the carbs just needed synched. Heres what Ive done. I removed the carbs, soaked them in carb soak, checked all the floats and jets cleaned everything and reinstalled. Synched carbs. Installed new plugs, bike has great spark. installed new fuel filter, and checked flow volume of fuel pump and works great.Plenty of pressure at carbs. AIr filter is new. Bike idles perfect, but boggs at 2500 rpm like its running lean. There is a hose connection at the carbs where there is no hose running to it. Cant figure out whats supposed to connect to it, all the vaccuum emissions hoses are connected to the carb, but there is a 5/16 male end with no hose is sight. The connecter tees off and connects to all other carbs with O-ring sealed hard plastic tubes, not sure if that matters or not. I think its just a fuel vapor vent. And am not sure if that would affect engine or not. Please help

Answer
Those are just vents like you thought.  It sounds like the bike is running lean.  Try applying a little choke as it leans out and see if it doesn't run a little better.  If it does, it's definitely a lean problem and you need to find out what's causing it.  I'm guessing the main jets are still partially plugged or the air passages inside the carbs are plugged.  You will probably have to disassemble the carbs and soak them to get them clean.  Make sure to blow out all of the passages you can see and check all the jets to make sure you can see through them. It's also possible the floats are set too low.  

Regards
Rich