4• Clean the four fuel strainers after every 120 hours flying time, and oftener, if necessary. The strainers should be cleaned immediately when irregular operation of either engine develops. 

For the location of the strainers and instructions .for cleaning them in flight, see Fig. XXVII on the following page. 

5. Make certain that pressure in fuel system does not exceed 25 lbs. per sq.in. when filling from external pump. 

6. Do not feed engines from a tank containing less than 12 gallons of fuel as the outlet is nearly uncovered with this amount of fuel still in the tapk, and with the ship at a 30° angle of pitch. 

The various operations which can be performed with the system, together with the proper settings of the valves, are described in Figures XXVIII-a thru XXVIII-j for K-3 thru K-10 airships, and in Figures XXIX-a thru XXIX-j for K-11 and future. 

## C. RECOMMENDED CARBURETOR ADJUSTMENT 

a Run engine at 400 RPM. 

b Cylinder head temperature should be normal. 

c Have good plugs in engine. 

d Have mixture control FULL RICH. 

e Note RPM. 

f Rapidly move mixture control from FULL RICH to IDLE CUT OFF positfon. Catch the engine before it stalls. 

(g) Note RPM. 

1. If large gain in RPM - Carburetor is set too rich. 

2. If loss in RPM - Carburetor is set too lean. 

3. Desired - gain of from 0 to 10 RPM. 

The desired setting is the RICH BEST POWER setting for the carburetor at the idle speed of the engine. 

