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JohnF2015, Small Engine Technician
Category: Small Engine
Satisfied Customers: 1107
Experience:  Owner/Service Technician at S & J Small Engines
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My Mc Culloch model 300 chain saw started with many tries

Customer Question

My Mc Culloch model 300 chain saw started with many tries and ran for about 30 seconds after I went all through it and replaced the filters, filed and gaped the points. It has new fuel and a thorough cleaning. The plug was also gaped and cleaned. It will turn over easily without the plug in, but I can only pull it over once with it in. Why is the compression so high? Could the exhaust have blocked up so fast?
Thanks for any help.
Submitted: 1 year ago.
Category: Small Engine
Customer: replied 1 year ago.
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Expert:  JohnF2015 replied 1 year ago.

Hi, my name is***** will be assisting you.

This sounds like the carburetor may be over fueling which would cause the machine to be extremely hard to pull after the first pull. It will cause excess compression due to the excess fuel in the cylinder. Have you pulled the plug and checked for excess fuel when the engine is cranking over hard? If you remove the plug when it is doing this and crank the engine once watch for fuel to blow out of the plug hole this is a good indication that the carburetor is over fueling. The most likely problem would be a stiff or cracked diaphragm inside the carburetor that would either hold the inlet needle open too long or allow fuel to pass through it when it shouldn't be.