Small Engines (Lawn Mowers, etc.): 19.5 h.p briggs, head gaskets, keyway

Question

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Followup To

Question -
I have a craftsman tractor with a 19.5 H.p turbo cooled  twin cyl engine.  The engine has just started surging excessively, when I start to pull the choke and its at about half way it runs out fine..  Sounds like lean fuel condition?  I replaced all fuel lines, filter, rebuilt the carb and the fuel pump, tried to adjust the governor and nothing seems to fix the problem.  It has 195 psi in each cylinder.  The engine seems to have good vacuum out of the crand case.  I pulled the flywheel to make sure the keyway wasn't slightly tweeked and all checks out fine.  I'm lost.  any other suggestions before i buy a new one?

Answer -
Did you replace the line for the fuel pump?  The line that runs to the engine block?

Did you clean the valve breater?
Did you use and air compressor to blow through the carburetor orfices?

Let me know.
Eric

i blew out all the orfices and replaced the line going to the block, but I did not take the breather out so I will try that tomorrow.  Thanks.

Answer
You may want to remove the carb again and clean the orfices again with compressed air.  
The main jet on the carb is prone to causing your problem.

Also, check the see if all the headbolts are torqued.  I've heard of leaky head gaskets causing the problem as well.  Finally, check the intake manifold screws and gaskets.

Let me know what you find.
Eric