Armature Air Gap

TM 5-4240-501-14P IGNITION Magna-Matic Armature Air Gap Armature air gap on engines equipped with Magna-Matic ignition is fixed and can change only if wear occurs on crankshaft journal and/or main bearing. Check for wear by inserting a feeler gauge 1/2" (12.7 mm) in width at points between the rotor and armature. Minimum feeler gauge thickness is .004" (0.1 mm). (Keep feeler gauge away from magnets on rotor or you will have a false reading.) Fig. 47. Fig. 47 - Checking Armature Gap Magna-Matic Ignition Remove Rotor The rotor is held in place by means of a Woodruff key and a clamp on later engines, and a Woodruff key and set screw on older engines. Fig. 48. THE ROTOR CLAMP MUST ALWAYS REMAIN ON THE ROTOR (UNLESS THE ROTOR IS IN PLACE ON THE CRANKSHAFT AND WITHIN THE ARMATURE) OR A LOSS OF MAGNETISM WILL OCCUR. Loosen the socket head screw in the rotor ecoup, allowing the clamp to loosen. It may be necessary to use a puller to remove the rotor from the crankshaft. On older models, loosen the small lock screw, then the set screw. Fig. 48 - Rotor Install Rotor If rotor has a set screw, Fig. 48, Illus. 2, place the Woodruff key in keyway on crankshaft, then slide rotor onto crankshaft until the set screw hole in rotor and crankshaft are aligned. Be sure the key remains in place. Tighten the set screw securely, then tighten the lock screw to prevent set screw from loosening. The lock screw is self-threading and the hole does not require tapping. If rotor has a clamp, Fig. 48, Illus. 1, place the Woodruff key in place in crankshaft, align keyways in rotor with Woodruff key. If necessary, use a short length of pipe and hammer to drive rotor onto shaft until .025" (0.64mm) feeler gauge can be inserted between rotor and bearing support. Split in clamp must be between slots in rotor. Tighten clamp lock screws 60 to 70 inch pounds (.7 - .8 kg m or 6.8 - 8.0 newton m). Fig. 49. Fig. 49 - Install Rotor Adjust Rotor Timing The rotor and armature are correctly timed at the factory and require timing only if the armature has been removed from the engine, or if the cam gear or crankshaft has been replaced. If necessary to adjust, proceed as follows: With the point gap set at .020" (0.5 mm) turn the crankshaft in normal direction of rotation until breaker points close and just start to open. Use a timing light or insert a piece of tissue paper between the breaker points to determine when points begin to open. With the three armature mounting screws slightly loose, rotate the armature until the arrow on armature lines up with the arrow on rotor as shown in Fig. 50. Align with corresponding number of engine model. On Models 9, align with 9, etc. Retighten armature mounting screws. 2 13