It is recommended that a new coil be selected from stock and used as a master coil to calibrate the tester. If the tester is set up with a "good-bad" range or "variable spark discharge gap", it can be used with whatever primary input is required to bring it into the desired range.

If the coil does not test to specification, the flywheel will have to be removed to replace the coil.

The high tension wire can be removed from the coil by twisting the wire in a counterclockwise direction.

ELECTRICAL EQUIPMENT

ELECTRICAL WIRING CIRCUITS NOTE: Beginning with engine serial No. 3981420 the standard wiring circuits of all 72 volt electrical equipment for Models S-10D and S-12D is negative ground polarity, instead of the previously furnished positive ground. Model S-14D, always was negative ground.

The wiring diagram, Fig. 13 (magneto ignition), illustrates a negative ground circuit. If polarity of Fig. 13, WIRING DIAGRAM (with Magneto Ignition) motor-generator is for a positive ground circuit, termi nal connections at ammeter and battery are just reversed from those illustrated.

MI-1109-2

To check if the generator is charging, it is only necessary to observe the ammeter that is connected in the battery circuit. If it shows a charge, the system is functioning properly. If it shows a discharge, remove the load connected to the 'L' terminal until the battery current is restored and the ammeter does register a charge.

Periodically inspect motor-generator and external wiring for conditions which may affect its operation.

Bearings are pre-lubricated, therefore no external oiling is required.

Inspect the brushes for wear, approximately every 200 hours of operation. If they are worn to less than half their original length, they should be replaced.

Battery ignition engines, are wired in accordance with Fig. 14. This type ignition system has always been wired negative ground. Battery is not furnished by Wisconsin Motor Corporation.

MOTOR-GENERATOR OPERATING INSTRUCTIONS

The combination motor-generator functions as a cranking motor when the starting switch is closed. When the switch is open and the engine is running, the unit will function as a generator. The generator output and circuit voltage for the various battery and operating requirements are controlled by a current-voltage regulator mounted to the generator.

The total electrical output of this 12 volt combination motor-generator is 12 amperes. However, all of the current is not taken off of a single terminal. There are two terminals on the current-voltage regulator, illustrted in Fig. 1.5. for distributing the generator output. One terminal is marked 'BAT' and a wire is connected from it to the battery, thru an ammeter. The other terminal marked 'L' is for a battery ignition system, if applicable, and for operating lights or any other customer accessory. For a continuous load, not more than 5 or 6 amps should be taken from this terminal if engine has magneto ignition. With battery ignition, maximum draw should be 3 or 4 amps, since 2 amps is required for the ignition system. Current from the 'L' terminal is continuous and is not affected by the regulator windings. Whereas, the current to the 'BAT' terminal goes thru the regulator windings and is controlled to keep the battery charged.

HIGH TEMPERATURE SAFETY SWITCH
As a safety precaution against overheating, engines can be equipped with a high temperature switch. The switch is mounted to a cylinder head bolt, opposite the spark plug at the take-off end.

When cylinder head temperature becomes critically high, the safety switch will automatically stop the engine by shorting out the ignition system. A waiting period of about 10 minutes will be required before the switch has cooled off sufficiently to restart the engine. An overheated engine will score the cylinder walls, burn out connecting rod and crankshaft bearings, also warp piston and valves. The cause of the overheating condition will have to be remedied before the engine is restarted. See Engine Overheats paragraph in Troubles, Causes and Remedies section.

A service kit is available for installation on engines in the field. Refer to parts section in rear of manual for mounting location and illustrated parts list.

SPARK PLUG
The spark plug should be removed periodically, cleaned and re-gapped. The width of the gap between the points of the two electrodes must be very carefully and precisely set, because incorrect settings will have an adverse affect on engine operation. Check spark plug gap with a wire type gauge and regap as shown in Fig. 16.