the engine. However, the air silencer or air inlet housing must be removed. CAUTION When  a  blower  on  an  engine  is  being inspected  with  the  engine  running,  keep  your fingers and clothing away from moving parts of the  blower.  RUN  THE  ENGINE  AT  LOW SPEED ONLY. Dirt or chips, drawn through the blower, will make deep scratches in the rotors and housing and throw up burrs  around  these  abrasions.  If  the  burrs  cause interference  between  rotors  or  between  rotors  and blower housing, remove the blower from the engine and dress down the parts to eliminate this interference. Replace the rotors if they are too badly scored. Oil on the blower rotors or on the inside surfaces of the blower housing indicate rotor shaft oil seal leaks. To confirm your finding, run the engine at a low speed while shining a light into the rotor compartment. A film of oil radiating away from the rotor shafts shows the oil seal  leakage. A worn blower drive results in a rattling noise inside the blower. You can detect this condition by grasping the top rotor firmly and attempting to rotate it. The rotor may move from three-eighths to five-eighths inch, measured at the lobe crown. When released, the rotor should move back at least one-fourth inch. If the rotor cannot be moved this distance or if the rotor moves too freely, the flexible  blower  drive  coupling  should  be  inspected  and if necessary, replaced. If a check shows the drive coupling to be worn, remove the blower drive assembly from the cylinder block end plate. After the blower has been removed from the  engine,  remove  the  drive  gear  hub  bearing support-to-cylinder  block  end  plate  bolts. Loose  rotor  shafts  or  damaged  bearings  will  cause rubbing  and  scoring  between  the  following  components: the crowns of the rotor lobes and the mating rotor roots, the rotors and the end plates, or the rotors and the blower housing.  Generally,  a  combination  of  these  conditions exists. Excessive usually  results length. backlash  in  the  blower  timing  gears in  rotor  lobes  rubbing  throughout  their To correct any of the above conditions, remove the blower from the engine and either repair it or replace it. The   blower   inlet   screen   should   be   inspected periodical  y  for  dirt  accumulation.  After  prolonged operation,  dirt  accumulation  affects  the  airflow.  Wash the screen thoroughly in clean fuel oil and clean it with a stiff brush until no dirt remains. The air box drains should always be open. Check them regularly and make sure the passages are clean. If the liquid collects on the air box floor, a drain tube may be  plugged.  Remove  the  cylinder  block  handhole covers. Wipe the dirt out with rags or blow it out with faltered compressed air. Then remove the drain tubes and connectors  from  the  cylinder  block  and  clean  them thoroughly. Blower  Removal  and  Disassembly After you inspect the blower and determine what you need to do to recondition it, remove and disassemble the   blower.   Follow   the   instructions   in   the manufacturer’s  maintenance  and  repair  manual. After you remove the assembly, disassemble it and be careful not to damage any parts. Use the proper tools and  follow  the  recommended  disassembly  procedures, particular  y  when  the  blower  drive,  driven  gears,  and timing gears from the rotor shafts are removed. Pull them from the rotor shaft at the same time or you will damage  the  rotors. Cleaning,  Inspecting,  and  Reassembly After  the  blower  has  been  disassembled,  wash  all the parts in cleaning solvent or clean fuel oil. Then blow-dry them, using filtered compressed air. Inspect the  parts  before  reassembly. Wash the bearings by rotating them by hand in either cleaning solvent or fuel oil until they are free from grease and foreign matter. Clean the balls (or rollers) and races by directing air through the bearings, at the same time, rotating them by hand. Do not spin the bearing with air  pressure. After  thoroughly  cleaning  the  bearings,  rotate  them again  by  hand  and  inspect  it  for  rough  spots.  The bearings  should  run  free.  They  should  not  show indications  of  roughness.  The  double-row  bearings  are preloaded and have no end play. A new double-row bearing will seem to have considerable resistance to motion when revolved by hand. Check  oil  seals  in  the  end  plates.  If  necessary, replace  them,  when  the  blower  is  being  reconditioned which is the recommended time to install new seals. 5-31