Warner Engine Handbook:

Service Inspection and Maintenance

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Section VII - Service Inspection and Maintenance

1. General

a. The work outlined in this section consists of periodic inspection, cleaning, servicing, lubricating, adjusting, and such maintenance work as is associated with the routine inspection system. For pre-flight inspection refer to Section on Starting and Normal Operation.

b. The necessary tools for this work may be found listed immediately preceding Section VIII of this publication.

c. Tightening nuts is one function of periodic inspection. Failures of nuts, bolts, and studs have been traced to excessive force in tightening. Therefore proper torque values should be used on all threaded parts. See torque limits in Table of Limits Section XIII of this manual.

2. Inspection and Maintenance

a. Daily

1. Inspect for evidence of engine throwing oil.

2. Inspect all oil plugs and drain cocks for proper safetying.

3. Inspect carburetor and fuel line connections.

b. 25-Hour


We recommend the following inspection routine be performed at least every 25 hours. Such regular inspection will give the most satisfactory engine performance and disclose defects otherwise likely to cause engine trouble. An engine that has been properly cared for will give much more satisfactory service, the time between overhauls will be lengthened and the total life of the engine will be considerably increased.

1. Check all mounting bolts, especially when rubber bushings are used.

2. Inspect all oil lines for: leaks, particularly at connections; security of anchorage; wear, due to chafing or vibration; dents or cracks.

3. Check all external nuts and bolts for tightness, immediately replacing cotter pins and lock wires when they have been removed for any purpose.


The bolts or nuts holding the intake pipes to the cylinders should not be tightened excessively as this will deform the flanges and cause leaks.

4. Check throttle, mixture and spark controls, making sure that the full movement of the controls in the cockpit corresponds to the full movement of the controls at the engine. Adjustments may be necessary where wires and springs are used to make control connections.

5. Check the ground wire and switch wire connections when the magnetos are used, at the engine and at the switch. It is very important that these connections be tight and that there are no breaks in the wires. This is to prevent accidental starting of the engine should the propeller be turned while the airplane is standing on the ground with the ignition switch on "off".

6. Check all high tension wires, to be certain that the insulation is not being chafed anywhere by sharp edges.

7. Spark Plugs

(a) Examine all spark plugs for tightness in the cylinder, for cracks in the core and for leakage between the core and the shell.

(b) Do not attempt to disassemble any spark plugs or set up gaps, as these gaps should be repaired by an authorized service station when the gap reaches .028, which will usually take 300 hours or more of flying. Improperly assembled spark plugs are likely to overheat and to cause serious damage to the engine.

(c) If a spark plug does not screw freely into the head, there either may be a burr on the thread of the plug, or the thread in the cylinder may be closed slightly, requiring cleaning of the thread with a spark plug tap.

(d) Check spark plug terminals.

8. Oil magnetos with 5 to 8 drops or good grade oil at the drive end, and slightly less at the rear end.

9. Remove rocker arm housing covers and wipe out rocker box. Inspect valve gear in regard to springs, spring washers, security or retaining split cone keys, rocker arms, etc. The rocker arms and rollers must move freely, and the rollers should be lubricated with a few drops of light oil. 0il exhaust valves with light oil.

10. Grease rocker arm shafts with a grease of good quality and high melting point. Ball bearing rocker arm lubricants, which have been round satisfactory by the Warner Aircraft Corporation, are listed in Section I, Table II of this book.


Grease containing graphite, asbestos, or other filler must never be used, as serious damage to the ball bearings in the rocker arms will result from use of such lubricants.

11. During inspection it will be well to remove the push rods and lubricate the ball ends thoroughly with rocker arm grease. Inspect push rods for wear and straightness.

12. Drain oil by opening the pet cock or plug at the bottom of the oil tank. The tank and engine should be flushed with clean light oil if grit is found in the old oil.

13. Remove and clean all removable oil screens. Clean sumps also.

14. Fill oil tank as specified on filler cap of oil tank after drain plug has been replaced and has been secured with a lock wire.

15. Check tappet clearances, which should be .010" to .012" for the intake and exhaust valves when the engine is cold. Proceed as follows:

(a) Turn the propeller forward until the Intake valve on cylinder No. 1 closes, then turn propeller an additional 120 degrees (1/3 of full turn) which brings the piston to the top center.

(b) Insert the feelers between the valve stem and the rocker arm roller for measuring. Make adjustments if the clearance is found to be below .010" or above .012".

(c) When cylinder No. 1 has been adjusted, turn the propeller forward 120 degrees beyond the closing of intake valve on cylinder No.2. Then check clearance of this cylinder.

(d) Continue this until all tappets are checked and adjusted.

16. Inspect carburetor and fuel line connections for fuel leakage, paying particular attention to drain plugs, passage plugs, and parting surface between body castings. Inspect all safety wiring on carburetor.

17. Remove float chamber drain plug and remove fuel strainer plug and strainer, and clean. Flush out water and sediment by allowing fuel to flow through strainer and drain plug openings.

18. Grease the rocker arms using the approved rocker arm lubricant.


Use only enough grease to fill the chamber in the rocker arm as an excessive accumulation of grease in the rocker boxes may lead to valve failure.

c. 50 Hour

1. Magneto

(a) Remove magneto breaker cover and check clearances between contact points when held wide open by the cam. The clearance should be .010" to .014", the most satisfactory .012".

(b) Put 20 to 30 drops of lubricating oil into the oil cup on the magneto front plate, and 5 to 8 drops into the oil cup on the magneto coil cover. Avoid over oiling.

(c) Examine the felt wick at the bottom of magneto breaker clip to make sure it is moist with oil. If oil appears on the surface of the felt when squeezed with the fingers, no additional lubricant is needed. If it is dry, moisten it with lubricating oil.

2. Inspect all ignition wiring for security of attachment.

3. See that inter-cylinder baffling is properly fastened and does not rub cylinder fins.

4. Inspect cylinders for damaged or broken fins.

5. Inspect induction system for security of attachment, leaking gaskets, broken studs, and leaks in the pipes.

6. Check carburetor heater (if installed) and air scoop for security.

7. Inspect thrust bearing nut and tighten if necessary.

8. Inspect cylinders for general condition.

9. Check compression an all cylinders by removing one spark plug from each cylinder except the cylinder to be tested. Swing the propeller by hand. The compression of the cylinder being tested can be judged by the amount of resistance offered. All cylinders should be checked in a similar manner, and all should "feel" the same. Check in the firing order which is 1-3-5-7- 2-4-6. All cylinders will come up on compression once in every two revolutions and an equal distance apart.

d. 100 Hour

1. Replace all sparks with new or reconditioned plugs of approved type. Inspect all spark plugs for gap clearance.

2. Carburetor

(a) Inspect parting surfaces between body castings for leakage and check all nuts and bolts on carburetor for tightness.

(b) Strainer assemblies, strainer plugs, or plugs marked "drain" should be replaced if found in bad condition.

3. Required Tools List

Tool Kit for Models SS50 and SS50A Engines

Part No. Part Name No. Req.
FA-23 Gage - Feeler (Bonney FA-23) 1
FA-26 Pliers - 6" Combination (Bonney B6) 1
FA-27 Screwdriver - 12" (Bonney W06) 1
FA-28 Tool Container - Canvas 1
FA-30 Tool - Valve Supporting 1
FA-33-A Wrench - Cylinder Base Nut (with Handle) (Bonney X-1241) 1
FA-34 Wrench - Magneto Breaker Setting (Furn. with magneto - Scintilla 4-490) 2
FA-35 ** Wrench - Propeller Nut (Bonney 810 C) 1
FA-36-2 Wrench - Socket with 7/16" Socket and Handle (Bonney Socket T14, Handle 7750 and Cross Handle T32) 1
FA-37 Wrench - 3/8" and 7/16" Open Ends (Bonney 1723) 1
FA-39 Wrench - 5/8" and 3/4" Open Ends (Bonney 1729 or Cornwell #EW 28) 1
FA-40 Wrench - 15/16" and 1" Open Ends (Bonney 408B) 1
FA-90 ** Wrench - Propeller Nut Inner (Bonney 809 S) 1
FA-91 ** Wrench - Propeller Nut Outer (Bonney 7889) 1
FA-105-A Tool - Valve Grinding 1
FA-111 Gun - Alemite - Hydraulic - (#6556) 1
FA-164 Tool - Valve Spring Depressing 1
FA-167 Wrench - Spark Plug 11/16" or 1
FA-259 Wrench - Socket 7/8" (Bonney LD28) 1
FA-171 Wrench - 1/2" and 9/16" Box Socket (Bonney 2805L) 1
FA-11238 Wrench - 3/8-24 Cylinder Hold Down Palnut 1

Note **:  FA-35 is furnished for use with No. 7226 nut for Hamilton metal propeller or OX type wood propeller hub.

FA-90 and FA-91 are furnished for use with standard steel propellers.  The customer must specify which type of propeller is to be used so that the proper wrench may be furnished.

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