TM 5-4240-501-14&P STARTERS-Briggs & Stratton Gear Drive 12V & 120V CAUTION:  DO  NOT  clamp  motor  housing  in  a  vise  or strike  with  a  steel  hammer.    Starter  motors  contain  two powerful magnets which can be broken or cracked if the motor housing is deformed or dented. Activate the starter motor and note readings of ammeter and  tachometer  (RPM).    Note  length  of   starter   motor housing  as  shown  on  page  9  and  refer  to  Fig.    91.    A starter motor in good condition will be within specifications listed. Motor Housing Minimum Maximum Length Motor RPM Amperes 3-1/16" (77.8 mm) 6500 18 3-3/4" (95.3 mm) 6900 19 Fig.  91 - 12 Volt DC Starter Motor Specifications 120 VOLT AC STARTER MOTOR Connect the starter motor and ammeter as shown in Fig. 92. DANGER:   It  is  recommended  that  the  starter  motor  be Hi-Pot tested after final re-assembly. CAUTION: The performance test of  this  starter  requires the use of an ammeter, connected in the 120 volt AC line cord.  Extreme care should be used in making this test to minimize the hazard of electrical shock. Fig.  92 - Checking Starter Motor Performance Plug  the  electrical  cord  into  a  120  volt  outlet  and  press the     starter     motor     button.          Note     the     readings     of tachometer  or  sirometer  (RPM)  and  ammeter.  A  starter motor   in   good   condition   will   be   within   the   following specifications.  Fig.  93. Motor Housing Minimum Maximum Length RPM Amperes 3-1/2" (88.9 mm) 6500 2.7 Fig.  93 - Starter Motor Specifications If either the 120 VAC or 12 VDC starter motor does not perform  satisfactorily,  the  following  should  be  checked and corrected if necessary. 1. A  binding  or  seizing  condition  in  the  starter  motor bearings. 2. Starter motor brushes sticking in brush holders. 3. A dirty or worn armature commutator or brushes. 4. A shorted, open or grounded armature. A. Shorted   armature   (wire   insulation   worn   and wires  touching  one  another).    Will  be  indicated by low or no R.P.M. B. Open  armature  (wire  broken)  will  be  indicated by low or no RPM. C. Grounded  armature  (wire  insulation  worn  and wire   touching   armature   lamination   or   shaft). Will   be   indicated   by   excessive   current   or   no RPM. 5. A defective starter motor switch. 6. A  defective  starter  motor  rectifier  assembly.    (120 volt AC only). 7. Weakened magnets. DISASSEMBLY OF STARTER MOTORS Study    Fig.        84    prior    to    starter    motor    disassembly. Remove  thru  bolts.    The  drive  head  end  may  now  be removed.    Inspect  bushing  for  wear.    If  worn,  replace drive head end assembly.  Fig.  94. NOTE:  MATCH  MARKS  AND  THRU  BOLTS  MUST  BE PLACED IN THE SAME POSITION AS WHEN RELMVOVED OR INTERFERENCE MAY RESULT. (See  checking  starter  motor  drive  if  repair,  cleaning  or replacement of drive assembly is necessary.) Fig.  94 - Removing Thru Bolts 26