Small Engines (Lawn Mowers, etc.): Gilson Snowblower Engine Question, briggs stratton engine, briggs stratton

Question
QUESTION:   My Gilson snowblower with a Briggs & Stratton 4HP engine suddenly doesn't run as smooth as before.  What happens is it kind of misses and loses power with the choke all the way off.  It seems to run better with the choke half on.  And it doesn't matter whether I adjust the jet to run lean or rich, it always runs better with the choke half on.

 At first I thought it might be water in the carb, but I ran some alcohol through it and the symptons still persist.

 What ever could be the problem?

 Thank you!

Steve
ANSWER: What is the enigne model, type and code number so I can look up the carburetor?
Let me know.
Eric

---------- FOLLOW-UP ----------

QUESTION:   Thanks, Eric.  The model of my Gilson is ST 522 (5 HP, 22" cut), and the number stamped on the Briggs & Stratton engine is 130202 1893 01 85062607.

 Thanks again!

Steve

Answer
Have you tried removing the tank/carb assembly and cleaning the carburetor?  You carburetor is very simple but it can be a little challenging removing it.  Usually I remove the tank/carb, then remove the carburetor from the tank for cleaning.  Have you replaced the fuel pump diaphragm on the side of the carburetor?  You also should have an adjustment needle on the side of the carb.  Have you tried turning it out a 1/4 of a turn to see if the engine runs smoother?
Let me know.
Eric