WARM-UP PERIOD

The engine should be allowed to warm up to operating temperature before load is applied. This requires only a few minutes of running at moderate speed. Racing an engine or gunning it, to hurry the warm-up period, is very destructive to the polished wearing surfaces of piston rings, cylinder, bearings, etc., as the proper oil film on these various surfaces cannot be established until the oil has warmed up and become sufficiently fluid. This is especially important on new engines and in cool weather.

Racing an engine by disconnecting the governor, or by doing anything to interfere with the governed control engine speed, is extremely dangerous. The governor is provided as a means for controlling the engine speed to suit the load applied, and also as a safety measure to guard against excessive speeds, which not only overstrain all working parts, but which might wreck the engine and possibly injure bystanders.

All parts of the engine are designed to safely withstand any speeds which might normally be required, but it must be remembered that the stresses set up in rotating parts increase with the square of the speed. That means that if the speed is doubled, the stresses will be quadrupled, and if the speeds are trebled, the stresses will be nine times as great.

Strict adherence to the above instructions cannot be too strongly urged, and greatly increased engine life will result as a reward for these easily applied recommendations.

STOPPING ENGINE

The breaker box on the side of the crankcase has a magneto ground switch for stopping the engine. Depress and hold down until engine stops. Engines with motor-generator or battery ignition have an ignition switch on control panel, "To Stop Push In".

If the engine has been running hard and is hot, do not stop it abruptly from full load, but remove the load and allow engine to run idle at 1000 to 1200 R.P.M. for three to five minutes. This will reduce the internal temperature of the engine much faster, minimize valve warping, and of course the external temperature, including the manifold and carburetor' will also reduce faster, due to air circulation from the flywheel.

CARBURETOR ADJUSTMENT (Fig. 6)

The main metering jet in the standard engine carburetor is of the fixed type and therefore no adjustment can be made.

On engines fumished with an adjustable jet carburetor, turn main jet adjustment in (clockwise), until it seats, then turn out (counter- clockwise) 2 1/4 turns. After the engine is started, warmed up for several minutes and running at normal operating speed, the needle valve should be readjusted for smooth operation.

MI-1105-2

4. Close choke on carburetor by pushing choke lever down (lever in horizontal position). Wind rope fully on sheave and pull briskly to turn crankshaft over.
Above 30 OF; open choke halfway if engine does not start after two or three pulls.
With starting motor; pull out ignition switch ('To Stop Push In'), and depress starter button.

5. After engine starts open choke fully (push lever up). Less choking is required in warmer weather or when the engine is warm, than when it is cold. Should flooding occur, open choke fully and continue cranking.
If all conditions are right, engine will start promptly after one or two attempts. Allow engine to warm up a few minutes before applying load, as prescribed in "'Warm-Up Period" paragraphs.
New engines should be "run-in" gradually to insure trouble-free service. Refer to "Starting and Operation , of New Engine", on the inside front cover of this manual, for correct 'running-in" procedure, with the exception that the initial break-in speed for the first half hour should be 1600 to 1800 R.P.M.

This adjustment need only be made the first time engine is started. In cold weather, starting may be facilitated by opening needle valve slightly more, then readjusted to normal running position after engine is started.

The correct amount of throttle plate opening for the proper low idle speed is obtained by means of the throttle stop screw. However, this is set at the factory so that no immediate adjustment is necessary. The idle adjustment is for smooth low speed operation and this adjustment, if necessary, must be made with the carburetor throttle lever closed. Normal idle setting is approximately 1 1/2 turns off seat.

For further information, refer to Zenith operating and service instructions in the rear of this manual

MAINTENANCE

AIR CLEANERS
These engines are provided with a dry element type air cleaner, as illustrated in Fig. 7A, with the previously standard oil bath air cleaner, Fig. 7, now furnished as optional equipment.

The air cleaner must be serviced frequently, depending on the dust conditions where engine is operated. Daily attention to the air cleaner is one of the most important considerations in prolonging engine life.

OIL BATH AIR CLEANER, (Fig. 7)
Once each week; the filtering element should be thoroughly washed in a solvent. Remove oil and clean out air cleaner bowl. Add fresh oil to the level line indicated on bowl, using the same grade oil as is used in the crankcase.

Service daily, if engine is operating in very dusty conditions. Detailed instructions are printed on the air cleaner.

Operating the engine under dusty conditions without oil in the air cleaner or with dirty oil, may wear out cylinder, piston, rings and bearings in a few days time, and result in costly repairs.

DRY ELEMENT AIR CLEANER, (Fig. 7A)
Service daily, if engine is operating in very dusty conditions. Remove cartridge and shake out the accumulated dirt (do not tap or strike element - it may become damaged). Wipe out dirt from inside cover.

Once each week; the filtering cartridge should be taken out and rinsed under a faucet with cold water, then wash by repeated dipping for several minutes in a solution of lukewarm water and a mild, non-sudsing detergent. Rinse in cold water from the inside out, and allow to dry overnight before installing. In cold weather, protect element from freezing until dry. Excessive smoke or loss of power are good indications that the element requires cleaning.

Do not use gasoline, kerosene or solvent for cleaning - Do not oil element.

After five washings or one year of service, replace cartridge. New cartridges are available at your Wisconsin Engine dealer. Refer to parts list section for replacement part number.

CRANKCASE BREATHER
A reed type breather valve is an integral part of the valve tappet inspection cover, as illustrated in Fig. 8. The valve maintains a partial vacuum in the crankcase, and thus eliminates internal crankcase pressure that would cause oil leaks at the seals, gaskets and breaker box. Keep complete breather system free from dirt. Clean breather valve by washing in solvent, and in reassembly mount with drain hole facing down.

Oil in breaker box may be the result of faulty breather action caused by dirt stuck between reed and seat. This condition can be remedied in the following manner: