Van's Aircraft RV-12, Maintenance Manual

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Rev.5
12-12
O
FF
I
DLE
S
ETTING
15. After warming the oil temp to the minimum required for takeoff power application,
run the engine to full throttle and verify the engine is developing proper power
with an indication of at least 4700 RPM.
16. Verify that both vacuum gauge readings are the same when the throttle is slowly
moved between near idle and full power. Use of damping valves (see Figure 30)
may be required to smooth out the vacuum gauge readings. Install valves if
required and slowly close them until the vacuum gauge readings stop fluctuating
rapidly.
If the vacuum gauge readings are not the same, shut down the engine and
verify that the choke controls on both carburetors are in the full off position. Also
verify that both throttle cable leads (see Figure 27) are resulting in full travel of
the throttle arms to the full throttle position on both carburetors. If both are
satisfactory move to step 17 for making adjustments.
17. Determine which carburetor has the higher vacuum reading. Loosen the aft nut
on the off idle adjustment hardware of the carburetor with the higher vacuum
(see Figure 27) and then tighten the fwd nut. This will adjust the throttle (for this
carburetor) open an additional amount.
18. Restart the engine and run the engine through the middle of the throttle range.
Repeat the adjustment done in step 17 until the vacuum gauge readings for both
carburetors are closely matched. If you go too far and the carburetor that you
have been adjusting ends up having a vacuum gauge reading lower than the
other reverse the adjustment and bring it back to where the vacuum gauge
readings match. Once the off idle vacuum gauge readings are balanced confirm
that the nuts on the throttle cable locking hardware are tight on both carburetors.
I
DLE
S
PEED
A
DJUSTMENT
▲ WARNING: D
O NOT ADJUST THE IDLE SPEED SCREWS MORE THAN
1/2
TURN EITHER WAY TO ACHIEVE THE PROPER IDLE SPEED
! I
F A SETTING OF MORE THAN
1/2
TURN IS REQUIRED
,
REPEAT
S
TEPS
1-8.
I
F NO SATISFACTORY RESULT CAN BE ACHIEVED INSPECT THE IDLE JET FOR
TRANSLUCENT
,
JELLY
-
LIKE CONTAMINATION AND FREE PASSAGE
. C
LEAN AS
REQUIRED
.