Small Engines (Lawn Mowers, etc.): Honda Harmony II Engine Quits, carburetor body, adjustment screws

Question
My Honda Harmony II (HRR216)has been working great for the past 2.5 years.  Today, about 5 minutes into mowing the engine started running rough, backfired several times, blew off the air filter cover and then quit.  I cleaned the air filter, replaced the cover and the mower started fine.  Two minutes later the same thing.  I noticed the plastic air filter cover is not sitting tightly against the casing (obviously since it blew off).  I tried to MacGyver it in place with some tape, but two minutes later same result.  Is this an air flow problem or is the air filter blowing off as a result of something else?  TIA.

Answer
Hello Steve:

This Problem can be Caused by Seeral Things. 1- The Valves need to be Adjusted. When the Engine Heats Up, the Valve Clearance is Closer than when the Engine is Cold and this Allows for the Backfire. 2- Timing Belt has Jumped a Tooth and has the Timing Off. 3- A Bad Spark Plug 5- The carburetor Not Metering the Gas Properly to the Engine. For this you need to  Remove, Disassemble and Soak the Carburetor Overnight in Carburetor Cleaner (I Use Gunk). I have Found that Most People can Use a Breakdown/IPL and Disassemble the Carburetor Enough for Proper Cleaning. You Only have to Remove the Bowl, Float Pin, Float and Needle Valve and Any Adjustment Screws that Go Into the Carburetor Body. The Welch Plugs Do Not have to be Removed. Then Soak the Carburetor Body and Parts in a 1 Gallon Can of Gunk Carburetor Cleaner Overnight. The Can has a Parts Tray Inside it for the Small Parts. Once the Carburetor and Parts are in the Cleaner, you can Replace the Lid for Safety and to Prevent Accidential Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required. From your Description, it Sounds like a Bad Spark Plug or the Carburetor May be the Cause. If the Plug and Carburetor are Good, then I Suggest you Check the Valves and the Timing Belt. You can View a Breakdown/IPL of the Mower at this Site Addy, http://hayward.arinet.com/scripts/EmpartISAPI.dll?MF&app=ASP&lang=EN&TF=Mainfram... and Select the Catalog American Honda. Then Select Lawn Mower. Then Scroll Down to your Model Mower and Select it. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John