Re: 305 carb issues
Guys the secondary air doors have a little spring on their pivot shaft, that is the main thing that closes them. The vacuum break keeps the secondary air doors closed when the choke is on and under high vacuum. Plus it dampens the rate of opening of the secondary doors when they do open. Aside from that everything that's been said is true.
It sounds like the spring is not wound, or there is a restriction that won't allow the shaft to turn. If the secondary doors pivot freely reset the spring.
It's a wicked pain in the butt to adjust.
The correct spring tension is 1/2 to 3/4 turn from free.
You can do it on the motor only if the tension spring is still caught on the adjuster, otherwise you'll need to take off the air horn (upper section) to see what to do. The adjuster looks like a recessed screw but it's actually a slotted barrel that the spring rides in. When you want to adjust it you release the hold down screw with a teeny torx bit, put the tensioner barrel where you need it and snug up the hold down. When the carb is on the motor the torx is facing straight down, it's really hard to get to without taking the carburetor off the engine.
Also the post that says the 305 won't open the secondaries very much is true. Even though the secondary throttle plates at the bottom are open, the secondary air flaps on top won't open til there's enough vacuum to pull them open. That only happens under maximum load and at higher RPMs. The primary side will feed that motor just fine almost all the time. The secondaries are just a little boost when needed.
