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Remove cover.
Clean points with a carborundum contact point stone. Then insert a hard finished card or piece of paper and close and open points. The paper will absorb any dirt or filings on the points. Adjust breaker points as follows:

a. Rotate crankshaft until points open to widest gap.
b. Loosen lock nut illustrated below until it is just snug.
c. Rotate breaker point screw to obtain .020" gap. d. When gap is .020" tighten locknut.
e. Replace breaker box cover.

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Clean spark plug and reset gap at .030" every 100 hours of operation. When worn out replace with A.C. GC-46, Autolite A71 or Champion J-8.

CAUTION: Blast Cleaning of spark plugs in machines that use abrasive grit is not recommended. Spark plugs should be cleaned by scraping or wire brushing and washing with a commercial solvent or gasoline.



Carburetors are adjusted at the factory and normally do not need adjustment unless they have been disassembled.

Initial Adjustment after Re-assembly

Turn needle valve clockwise until it just closes.
Valve may be damaged by turning it in too far.
Now open needle valve 1-1/2 turns counterclockwise. Close idle valve in same manner and open it 1/2 to 3/4 turns. This initial adjustment will permit the engine to be started and warmed up prior to final adjustment.

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Final Adjustment

Turn needle valve in until engine misses (lean mixture), then turn it out past smooth operating point until engine runs unevenly (rich mixture). Now turn needle valve to the mid-point between rich and lean so the engine runs smoothly.

Hold throttle at idle position, set idle speed adjusting screw until fast idle is obtained (1200 RPM). Hold throttle in idle position and turn idle valve in (lean) and out (rich) until engine idles smoothly. Then reset idle speed so that engine idles at 1200 RPM. Release throttle - engine should accelerate without hesitation, or sputtering. If engine does not accelerate properly, re-adjust needle valve to a slightly richer mixture.


The governor controls the engine speed from idle through the full operating range. Idle speed should be no lower than 1000 RPM and top no load speed should be no higher than 3800 RPM. See illustration to adjust governor.


The shorter spring keeps the engine on governor, even at idle speed. If moderate loads are applied at idle, the engine will not stall.


First make final carburetor mixture adjustments. Then place remote control in idle position. Hold throttle shaft in closed position and adjust idle speed screw to 1000 R.P.M. Release the throttle. With remote control in idle position, adjust upper elastic stop nut to 1200 R.P.M.


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



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