Small Engines (Lawn Mowers, etc.): 24 hp horizontal shaft motor backfire, electric fuel pump, horizontal shaft

Question
I removed the air filter housing and found 2 screws on top of the carb, 1 marked  L and one R. Only one could be adjusted by 1/4 turn. Did I indeed find the right screws I'm not sure? I turned the one in and used the motor. It was better but still backfired some upon shutting off. I can't let it run for 2 min before shutting down because it is on my boat and is a direct drive motor. Does this motor have a vacuum fuel pump? The numbers I found on the engine are GX670  TAFY GCAM 1007247. Thanks again Mike
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-----Question-----
I have a 24hp Honda on a mudmotor. I replaced the electric fuel pump with the recommended one. My motor now backfires when I shut it down and smells like it is running very rich. Any help is appreciated. Mike
-----Answer-----
 Hello Mike:

 Turn the High Air Mixture Screw IN 1/4 Turn. Are you Allowing a 2 Minute Cool Down for the Engine Before Shutting Off the Engine? Send me the Model and Type Code Off the Engine, Please. With these, I can Locate a Breakdown/IPL and Better Assist you. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John

Answer
 Hello Mike:

 Sorry for the Delay. Go to this Addy http://www.honda-engines-eu.com/en/service/spareparts/heepartscatalogue/index.js and Select the Model GX670 and the Type TAF and Click Search. You can View a Breakdown/IPL of the Engine from here. Check the Fuel Solenoid. Remove the Solenoid and Replace it with a Bolt 3/4" Long and the Same Diameter and Threads. Run the Engine. Check the Muffler for Blockage. Carbon will Collect in the Muffler and it Doesn't Allow the Muffler to Exhaust Properly. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John