L120 Won't Start without priming carb

   / L120 Won't Start without priming carb #11  
Yes. L series are vented via a center hole. Welcome.
 
   / L120 Won't Start without priming carb #13  
So what should Mr. Barnes do ?
Two things. Make sure he has the correct cap since it appears that model should have a vented cap. And the other thing is make sure the choke is closing completely. If that mower has the single throttle/choke control there is a good chance that the throttle cable has slipped in the clamp at the front of the engine and is now not completely closing the choke.
 
   / L120 Won't Start without priming carb #14  
All of the above….maybe try running it with the gas cap loose? but maybe check the valve lash too. Difficulty starting a cold small engine is one symptom of tight/no valve clearance. Google the clearance or check your manual for your specific engine.
 
   / L120 Won't Start without priming carb #15  
Late to the thread, but it may be bad fuel line between tank and fuel pump.... I had problems with hard start and after many hours of chasing things discovered fuel line had macroscopic holes in it and was drawing air instead of fuel.... Replaced fuel line between tank and fuel pump and problem solved....
 

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