Some air cleaners are not set up to allow for the breather bolts into them and are only held on by the three small carb front bolts. ¹⁾
For these breathers you would need to get a head breather kit and carb support bracket.
The breather kit routes the head vents to the ground while the carb support bracket keeps the carb in the intake.

Read more about the breather valve system here: Evo Crankcase Ventilation.

The breather valves are located in in the rocker box with their air outlets in the heads.
The breathers are one-way umbrella valves.
These exit crankcase vapors through vents in the top of the cylinder head into the air cleaner.
On each piston downstroke, crankcase pressure (air and oil mist) is routed up the pushrod tubes into the rocker box.
Collected air pressure and oil mist in each rocker box is routed up into a sealed cavity in the lower portion of the box.

This mixture passes up from underneath a rubber one-way valve sitting over the cavity inlet in each box.
The oil is designed to separate from the air by hitting the underside of the umbrella valve and dropping back down into the lower end.

Air pressure is designed to continue up past the umbrella valve and exit the hole in each head on the intake valve side. Air pressure escapes the head through the hollow bolts (one in each head) that hold the air cleaner mount.

^{2) 3)}