I was pulling my carbs off to send to RPM for a rebuild due to some nasty low rpm throttle response. I have the factory manual that shows a vacuum line going from the cdi box to a fitting on the intake boot for the #3 cyl. The manual had no mention of any other vacuum lines. Maybe Calif evap stuff that is now missing. I also noticed that on each carb there was a downward facing fitting the really looked a vacuum hose could be attached to it. The PO had a hose going to the CDI box from the #4 carb itself not from the intake boot. Was my problem caused by all these open vacuum hose fittings?
The vacuum ports you have to worry about are the 4 ports on the intake manifold.
2 of the 4 ports are occupied by the vacuum line to your petcock and vacuum line to the TCI box, the other 2 ports should be capped with the heavy rubber oem Yamaha caps and clamps. Don't use thin walled vacuum caps you can get at your auto parts store. The heat in that location will destroy light duty caps...you need the heavy walled oem caps, with clamps.
The TCI box (Transistor Controlled Ignition) on your '84 has a vacuum line that is part of the advance system for smog, and can be capped off with no issues. Often the diaphragm in the TCI box rots out and then leaks unmetered air into your intake manifold.
Do the suck test on this vacuum line. You should not be able to suck any air into this vacuum line. If so, cap it off.
Here's more reading on the TCI and DCI vacuum lines. : https://fjowners.com/index.php?topic=11690.0
If you have a Calif. model you have a vent on the carbs #1 and #4 that are connected to the two charcoal canisters that fuel tank vapors draw into. They should be capped if not used.
The downward facing ports on your carbs are the choke vents (not vacuum) They draw air into the choke circuit only when the choke is activated. You need short 14" hose lines on those ports running to the back of the engine.
You will also notice 2 larger hoses connected to T's between carbs 1/2 and 3/4, those are your fuel bowl vents, those also should have hose lines running to the back of the engine. Don't plug, kink or pinch these choke vents or bowl vent hose lines.
Good move on getting those carbs to Robert at RPM.
Hope this helps.
Pat
Thanks yet again for sharing your knowledge. Just capped of the vacuum fitting at the TCI box.