TM 1-1500-204-23-1 b. Depreservation.  Carburetors are depreserved to make them operational after they have been preserved for extended storage. Observe the following precautions. ·    Depreserve   float-type   carburetors   which   do not    employ    diaphragms    by    flushing    float chamber with the type of fuel used to operate applicable   engine,   then   drain   oil   and   fuel mixture  from  float  chamber.    Flush  until  all trace of preservative oil is removed. ·    Depreserve    diaphragm-type    carburetors    by draining oil from fuel chambers and passages and   flushing   with   fuel.      Fill   carburetor   with type  of  fuel  to  be  used  to  operate  applicable engine.  Soak diaphragm for at least 8 hours. This    restores    fuel    diaphragms    to    normal operating condition. c. Adjusting  Idle  Mixture  and  Idles  Speed      If  an engine   will   not   respond   to   idle   mixture   and   speed adjustment, it is an Indication that some other phase of engine  operation  is  incorrect.    Adjust  idle  mixture  and idle speed using the following procedures. (1) Make   idle   mixture   adjustments   with   oil and cylinder head temperatures at normal values. (2) Back idle speed stop off so that idle speed Is   controlled   during   adjusting   procedure   by   manually controlling throttle. (3) Retard throttle to designated rpm. (4) Screw   idle   mixture   in   or   out   in   small increments   as   required   until   proper   idle   mixture   is established. (5) After each idle mixture adjustment, increase     power     to     field     barometric     pressure     for approximately 1 minute to clean intermittent firing spark plugs caused by excessively rich or lean mixture. (6) Set idle speed stop to desired rpm. d. Repair   or   Replacement.      Repair   or   replace carburetor using the following procedures: (1) When  improper  operation  of  float-type carburetor   is   suspected,   perform   a   test   by   manually leaning   mixture   with   mixture   control   or   by   enriching mixture by use of primer.  Replace complete unit when changes in rpm, other than those within allowable limits, result. (2) When   difficulty   is   encountered   with   PD and  PR  series  Injection-type  carburetors,  attributed  to sticking   or   binding   of   automatic   mixture   control   unit, clean unit as follows: (a) Remove unit from carburetor, being careful not to remove seal or lockwire or loosen siphon locking nut. WARNING Dry-cleaning    solvent    is    flammable and solvent vapors are toxic.  Use P- D-680,   Type   II   Solvent   In   a   well- ventilated    area.    Keep    away    from open flames Avoid prolonged solvent contact with skin. (b) Wash     bushing     with     dry-cleaning solvent, Federal Specification P-D-680. (c) Dry thoroughly with compressed air. (d) Polish   bushing   sleeve   with   crocus cloth, Federal Specification P-C-458, until it is bright. (e) Blow   out   any   polishing   dust   that tends to cling to inside walls. WARNING Dry-cleaning    solvent    is    flammable and  solvent  vapors  are  toxic  Use  P- D-680,   Type   II   Solvent   in   a   well- ventilated   area.      Keep   away   from open     flames.          Avoid     prolonged solvent contact with skin. (f) Clean needle with dry-cleaning solvent,  Federal      Specification  P-D-680,  and  dry  with compressed air (g) When    needle    is    corroded,    clean with   dry-cleaning   solvent,   Federal   Specification   P-D- 680,  dry  with  compressed  air,  polish  with  crocus  cloth, Federal Specification P-C-458, and lubricate with grease molybdenum disulfide MIL-G-21164. (h) Reassemble  and  install  lockwire  or seal, if broken. 7-37