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CHANGE OIL (Crankcase)

Change oil after 5 hours of operation. Remove the oil drain plug. Drain oil while engine is warm. Replace drain plug. Remove oil filler cap or plug and refill with new oil. Replace oil filler cap or plug. Add oil regularly after each 5 hours of operation. Thereafter change oil every 25 hours of operation.

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Clean and re-oil the a-it cleaner frequently (every few hours under extremely dusty conditions). Clean and re-oil at least every 25 hours under normal conditions.

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  1. Remove wing nut and cover.

  2. Lift off foam element from base.

  3. Push down foam element as shown, and pull out

  4. A - Wash foam element in kerosene or liquid detergent and water to remove dirt.
    B - Wrap foam in cloth and squeeze dry.
    C - Saturate foam in engine oil. Squeeze to remove excess oil.
    D - Put screen inside element. Be sure sealing lip is over end of screen (top and bottom).

  5. Reassemble parts as shown. Screw wing nut down tight.


Grass or chaff may clog cooling system after prolonged service in cutting dry grasses or hay. Continued operation with a clogged cooling system causes severe overheating and possible engine damage. Remove blower housing and clean regularly.



Loosen thumb screw below filter bowl.

Remove and clean filter bowl and screen.

Open shut-off valve to see if fuel flows freely from the tank. IMPORTANT: If you find a gummy, varnish-like substance use alcohol or acetone to dissolve it.

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This industrial engine generally operates at constant speed and at relatively constant load. The use of regular automotive fuels under these conditions results in a gradual build-up of lead deposits in the combustion chamber.

This causes the engine to lose power and prevents the valves from seating properly. Removing the deposits is easy and will pay big dividends in reliability and increased valve life.

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  1. Remove cylinder head screws.
  2. Turn crankshaft until piston is at top of cylinder bore and both valves are closed. Scrape and wire brush the lead and carbon deposits from cylinder head and combustion chamber.
  3. Re-use cylinder head gasket only if in good condition. Replace cylinder head. Turn each screw in with wrench until screw head is lightly seated.
  4. Use socket wrench with 6 inch handle and turn all screws l; 4 turn. Tighten screws in sequence illustrated. Run engine approximately 5 minutes and retighten all screws approximately 1/4 turn.


[Source:  Briggs & Stratton Operating and Maintenance Instructions, Models 300401 to 300424, Form  270453-116, courtesy of Mike Decoteau]



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