Small Engines (Lawn Mowers, etc.): Honda GX670, carburetor body, internal passages


Question
QUESTION: Hi John,
Not sure if you are the right person to direct this question to.. But I have a Honda GX670 TXWX GCAM - 1025818 that seems to have a problem with the oil level switch. The motor lost its spark and after a bit of trouble shooting I disconnected the oil level switch and it got spark back again. (yes it has plenty of oil in it)What I would like to know is that by having this switch disconnected would it make the engine run rough?? it will not idle now and requires the throttle to be continuosly worked to keep it running. or with the switch disconnected would it run as normal but obviously without the low oil level cut out protection.. I am just wondering if I have another problem somewhere else that is why I ask.


ANSWER: Hello Mark:

Disconnecting the Oil Level Switch will Only Disable the Low Oil Shut Off and Not Effect the Engines Normal Operation. If the Engine is Running as you Described, then you May need to Soak and Clean the Carburetor. The Cost of the Cleaning Solution I Use is $30.00us @ Gallon (I Use Gunk). The Gallon Can Comes with a Tray for Small Parts and the Carburetor Fits Nicely. Most Times a Carburetor can be Soaked and Cleaned and with the Float, Needle Valve and Other Carburetor Components being Soaked in the Cleaner with the Carburetor Body; there are No Parts to Replace on this Carburetor. If you Soak and Clean this Carburetor and the Float Needle Valve Still Does Not Stop the Gas Flow Properly, then Purchase a Needle and Seat Kit and Replace it. The Following is a Basic File I Made for Cleaning Carburetors. Any Input is Appreciated. The Most Common Cause is; The Carburetors Internal Passages are Restricted by Varnish that Gas Forms Over Time. This Varnish is in Layers. To Properly Remove this Varnish you have to Soak the Carburetor. The Following is a General Instruction File for Carburetor Cleaning. Even though the Carburetor Looks Clean, the Internal Passages May be Restricted with Varnish that Gas Causes to Build Up over Time. I Suggest you Make Sure the Gas is Free Flowing to the Carburetor Inlet Port (if the Model does Not have a Fuel Pump). If the Gas is Free Flowing to the Inlet Port, then  **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 (if Applicable), Float Pin (if Applicable), Float (if Applicable), Needle Valve and Needle Valve Seat if Applicable. This is a Flat O-Ring Located in the Inlet Port the Float Needle Rests in. Use a Strong Wire with a Slight Bend to Remove the Old Seat. Sometimes a Small Pocket Screw Driver can be Use Also. The New Seat will have a Slightly Beveled Side and a Flat Side. The Flat Side goes Towards the Carburetor Body when Inserted into the Inlet Port. Spray the Seat with Spray Lubricant to make Installation Easier. The End of a Drill Bit that is Slightly Small than the Seat can be Use as an Insertion Tool. Wear Gloves or Use a Rag when Handling the Sharpened End of the Drill Bit. Remove 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 Accidental Spillage. Then Blow Out the Passages with Compressed Air.*** (Do Not Use High Pressure Air for the Zama Carburetors, they have Check Valves for the Primer and these are Usually Blown Out of the Carburetor if Not Careful. Allow the Zama Carburetor to Set on a Drip Pan and Dry)***. ****All the Carburetor Adjustments are the Same for Lawn Mower and Trimmers. There are Several Location for the Air Mixture Screws. The Idle Air Mixture Screws are Usually Located at the Top of the Carburetor Bowl and the Top of the Carburetor Body. If the Main Air and Idle Air Mixture Screws are Side by Side on the Side of the Carburetor, then the Idle Air is Nearest the Engine. The Main Jet Air Mixture Screw is Located in the Bottom of the Carburetor Bowl or Beside the Idle Air Screw on the Side of the Carburetor Body. Some of the Older Model Carburetors have the Main Jet Mixture Screw Straight in from the Top of the Carburetor Body (this is Rare anymore). If you have Cleaned the Carburetor (Disassembled and Soaked Overnight in Carburetor Cleaner (I Use Gunk). Then Blow Out the Passages with Compressed Air and Install a New Kit if Required. Now Setting the Air Mixture Screws:  ****Turn the Idle Air and Main Air Mixture Screws In Until SNUG **Do Not Jam** Then Reverse Both Screws 1 1/2 Turns. Holding the Throttle Full Open, Start the Engine. Turn the Main Air Mixture Screw Clockwise Until Proper Revs are Obtained. Occasionally you May have to Turn this Counter Clockwise to Achieve the Proper Revs. Now Allow the Engine to Idle. Set the Engine Idle Screw (Not Idle Air) so the Engine will Stay Running if Required. Now Set the Idle Air Mixture Screw so there is No Hesitation when Throttling from Idle to Full Throttle. Reset the Engine Idle if Required.**** If This Carburetor has a Single Air Adjustment. Use the Section Above that Pertains to Full Throttle RPM Air Mixture Screw and then Adjust the Screw if Required to Eliminate Any Hesitation when Throttling from Idle to Full Throttle. This file was Intended to Give you the Basic Carburetor Cleaning Instructions and May Not Reflect Your Carburetor Components. If you have Questions, Please Ask. You can View a Breakdown/IPL of the Mower/Engine at this Site Addy, http://hayward.arinet.com/scripts/EmpartISAPI.dll?MF&app=ASP&lang=EN&TF=Mainfram and Select the Catalog American Honda. If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.

Respectfully

John

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

QUESTION: Hello Again John,

Thanks for your previous reply I have not had a chance to check/clean the carby yet but will do that as soon as I am on days off. I did manage to work out that the oil level swith did not have anything to do with the rough running of the engine. One thing I did not mention before is that while running rough the motor is also back firing through the carb every now and then and was wondering if this could be a timing thing not that I have seen anywhere to adjust the timing on these motors.. Anyway thought I would just chuck that in... I will let you know how i go with the carby clean. Hopefully that is all it is.

Answer
Hello Again Mark:

From your Description it Sounds like the Valve Clearances are too Close and the Valves are Not Closing Properly or the Flywheel Key May be Damaged. 1- Try Setting the valve Clearance. The Following is a Basic File I made for Setting the Valve Clearances. Any Input is Appreciated. **I Do Not Use the Setting Called for by the OEMs. I have Found that the Following Works Best. Remove the Valve Cover (on the Dead Cylinder for Twin Cylinder Engines). Set the Cylinder you are Setting the Valves on to Top Dead Center on the Compression Stroke When Setting the Valve Clearance. Now Loosen the Valve Adjuster Locks and Set the Intake Valve Clearance to .004in -.006in and the Exhaust to .007in - .009in. I have had Better Performance Out of the Mowers and Less Burnt Valves Using these Settings. Be Sure the Piston is at TDC on the Compression Stroke.** On Some Engines you can Us a Straightened Coat Hanger and Feel the Piston. Be Careful and Dont Jam the Wire in the Cylinder. Usually the Piston will Push the Wire Out of the Spark Plug Hole with No Problems. 2- The Following is the Instruction File I Made for Removing the Flywheel from Most Mower Engines.  It is the Basics and if you have a Question, Please Ask. Any Input to Make this File Better is Appreciated. ***Disconnect the Coil Wire from the Spark Plug. Remove the Blower Housing (metal engine cover). Remove the Coil. Remove the Flywheel Nut or Starter Cup (Depends on the Model). Now Attach a Steering Wheel Puller to the Flywheel Using the Threaded Holes in the Flywheel. Tighten the Puller. Now Hit the Puller with a Hammer. Repeat this Procedure Until the Flywheel Pops Up or can be Lifted Off the Crankshaft. On Some Models you Can Not Use a Puller and Must Use a Pry Bar and a Pipe Cap that is Slightly Larger than the Crankshaft. Place the Pipe Cap Over the Crankshaft to Protect it. Place the Pry Bar Under the Thick Section of the Flywheel and Pull Up Against the Flywheel. **BE CAREFUL  DO NOT PUT A HOLE IN THE BLOCK UNDER THE FLYWHEEL** Now Hit the Pipe Cap that is on the Crankshaft (covered with the Pipe Cap). Repeat the Procedure Until the Flywheel can be Lifted Off the Crankshaft. *** Be Sure you have the Flywheel Torqued to the Proper Torque (I require the Model and Spec/Type Numbers Off the Engine to Provide the Proper Torque) and Set the Coil Gap to .020in.. If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Ratings and Comments are Greatly Appreciated. Thanks.

Respectfully

John