This vacuum box controls the second stage.
The 2 stage throttle valve gap is set at 0.05 mm (0.0020")
whith screw (1) in compliance with the 130 ± 10 main jet.
Coution! The throttle valve will stick if its gap is too small.

Give throttle valve 0.3 mm (0.012") tension with springloaded
stop pin.
Loosen counternuts.
Tighten the adjusting screw until the spring-loaded stop pin just touches
the locking lever.
Then tighten the adjusting screw by ½ turn more.
Coat adjusting screw with Loctite and tighten the counternuts.
If the tension is more than 0.3 mm (0.012"), the roller is jammed
in the gate.

Check diaphragm spring if maximum speed cannot be reached.
BMW 2.5 ltr.
Identification 0.4: Shorten diaphragm spring form 10 to 6 windings.
Identification 0.3: Diaphragm spring with 8 windlings.
BMW 2.8 ltr. - 3.3 L
Identification 0.4: Diaphragm spring with 10 windings.

Only applicable to replacements of diaphragm:
Detach connecting rod (1).
Remove cover.
Take out spring and diaphragm.

Check rod setting.
A = 65 mm (2.559")