2.  
Carburetor heat is supplied by a duct interconnected with a shroud mounted to the cylinder No. 4 exhaust manifold.  The duct can be removed by first removing the clamps retaining it to the air box and shroud fixtures.

3.  
Remove the screws securing the outboard shell of the shroud and slide it forward out of the main shroud support.

4.  
Remove the bolts securing the shroud to the exhaust stack.

71-60-00 Page 71-22 Issued: April 1, 1997
3G12

Figure 71-4. Induction System 
71-60-00 
Page 71-23 
Issued: April 1, 1997 
3G13 

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71-60-00 Page 71-24 Issued: April 1, 1997
3G14

CHAPTER

73

ENGINE FUEL SYSTEM

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CHAPTER 73 - ENGINE FUEL SYSTEM 
TABLE OF CONTENTS / EFFECTIVITY 
CHAPTER/ SECTION  SUBJECT  GRID NO.  EFFECTIVITY 
73-10-00  DISTRIBUTION  3G19 
Carburetor Maintenance Adjustment of Idle Mixture Adjustment of Idle Speed  3G19 3G20 3G20 
Engine Primer Installation Electric Primer Primer Jets  3G21 3G21 3G21 
73-20-00  CONTROLLING  3H1 
Adjustment of Throttle, Mixture and Carburetor Heat Controls  3H1 
73-30-00  INDICATING  3H3 
Fuel Pressure Gauge Fuel Pressure Sender Testing Troubleshooting (Fuel Pressure Gauge)  3H3 3H3 3H4 

73-Cont./Effec. Page 73-3 Revised: February 28, 2002
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73-Cont./Effec. Page 73-4 Issued: April 1, 1997
3G18
DISTRIBUTION.
CARBURETOR MAINTENANCE.

— WARNING —
THE USER IS RESPONSIBLE FOR REFERRING TO THE APPLICABLE VENDOR PUBLICATION(S) WHEN SERVICING OR INSPECTING VENDOR EQUIPMENT INSTALLED IN PIPER AIRCRAFT. (SEE INTRODUCTION, PAGE 5.)
In general, little attention is required between carburetor overhauls. However, it is recommended that the following items be checked during recommended inspection periods of the engine.
1.
Check tightness and safety of all nuts and screws which fasten the carburetor to the engine.

2.
Check all fuel lines for tightness and evidence of leakage.

3.
Check throttle and mixture control rods and levers for travel, tightness and safety.

4.
Clean the fuel inlet screen. (Refer to Figure 73-1.)

5.
Remove the plug at the aft position of the carburetor and drain any accumulation of foreign matter.

6.
Check carburetor air box for wear and full travel of heat door.

7.
Check the adjustment of the idle mixture and idle speed.

— CAUTION —
GROUND RUNNING WITH THE COWLING REMOVED: MAXIMUM
POWER GROUND RUNNING IS LIMITED TO FIVE MINUTES OR
CYLINDER HEAD TEMPERATURE OF 475°F, WHICHEVER IS
REACHED FIRST. AIRCRAFT WITHOUT CYLINDER HEAD
TEMPERATURE GAUGE MUST NOT BE OPERATED AT MAXIMUM
POWER WITH COWLING REMOVED. PROLONGED GROUND
RUNNING WITH THE COWLING REMOVED COULD CAUSE LOCAL
HOT SPOTS IN THE CYLINDERS AND IRREVERSIBLE ENGINE
DAMAGE.

Figure 73-1. Carburetor 
73-10-00 
Page 73-5 
Issued: April 1, 1997 
3G19 

ADJUSTMENT OF IDLE MIXTURE. (Refer to Figure 73-1.)
— WARNING —
WHEN PERORMING ENGINE WARM-UP INDOORS, PROVIDE A BARRIER ABOUT THE ENGINE TO PREVENT SERIOUS INJURY. ALSO PROVIDE ADEQUATE MEANS OF VENTILATING THE WORK AREA.
1.  
After performing the standard engine starting procedure, operate the engine for at least two minutes between 800 to 1200 RPM to insure proper engine warm-up.

2.  
Position the cockpit throttle control lever to obtain a reading of approximately 550 RPM on the tachometer with the idle mixture control at the full rich position.

3.
While observing the tachometer, slowly pull the mixture control towards the idle cut-off position.   The optimum mixture is obtained when the RPM increases slightly (10 to 50 RPM) prior to engine speed decreasing.

4.
Following the momentary increase in RPM, the engine speed will start to drop.   Immediately move the mixture control to the full rich position to prevent the engine from cutting out completely.

5.
Should these steps reveal that the idle mixture is not correct make the following adjustments and perform Steps 2 thru 4 again.

A.  With the engine set to idle at 550 RPM turn the idle mixture adjusting screw at the rear of the carburetor, clockwise, leaning the fuel mixture.  Continue to do this until the engine begins to run roughly, at which time the engine speed will decrease.
B.  Turn the adjustment screw counterclockwise until the engine runs smoothly again.  Continue to turn the screw in the same direction until the engine begins to run roughly once more.  At this point, the fuel mixture will be too rich and engine speed will decrease again.
　
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