content_image/545148.jpg
CAUTION: An idle speed that is too low results in gearbox damage, and if an idle speed is too high, the engine is harder to start. Start the engine and verify the idle speed. If the idle speed is too high or too low, adjust accordingly with idle speed adjustment screw (2). Check the operational idle mixture of the engine. If necessary, adjust with the idle mixture screw (6). 

## Pneumatic Synchronization 

Mechanical synchronization should have already been accomplished. The two carburetors are adjusted to equal flow rate at idling by use of a suitable flow meter or vacuum gauges (1). 

There are two possible methods to connect test equipment. One option is to remove hex screw (6) M6 x 6 from the intake manifold (7) and connect the vacuum gauge(s). [Figure 11-26 and  Figure 11- 29]  Remove the compensating tube (2) with attached hoses (12) (connection between intake manifolds) and plug the connections in the intake manifolds. The other hook up option is to remove the compensating tube hose (2) from the push-on connection (5) after removing the tension clamp (4). Using the push-on connection (5), install a flexible rubber hose (8) leading to the vacuum gauge (1), using the balance tube (4). Install the other flexible rubber 

hose leading to the vacuum gauge. [Figure 11-29]  Before proceeding any further, secure the aircraft on the ground using wheel chocks and ropes. 

WARNING: Secure and observe the propeller zone during engine operation. 

Start the engine, verify the idle speed, and make any necessary corrections. If a setting correction of more than ½ turn is required, repeat mechanical synchronization to prevent too high a load on the idle stops. If the idle speed is too high, the maximum the idle screw can be unscrewed is a complete turn. If no satisfactory result can be achieved, inspect the idle jets for contamination and clean if necessary. 

Caution: Also check for translucent, jelly-like contamination. Inspect for free flow. 

Once the proper idling speed has been established, it is necessary to check the operating range above the idle speed. First, establish that the engine is developing full takeoff performance or takeoff rpm when selected in the flightdeck. Then, the setting of the operating range (idle to full throttle) can be checked or adjusted. 

<img src='content_image/545148.jpg'>

