Small Engines (Lawn Mowers, etc.): MURRAY RIDING MOWER, safety switches, gas tank

Question
QUESTION: Hi John..still having troubles with this Murray..I adjusted the valves as you said .. 13hp OHV130-206810D  model 40541x99C
the original problem was backfiring w/ loss of power..you thought it might be flywheel sheared key or valves.I adjusted valves as you said..now it shuts off after only running a minute or less~before it did not do this..it would run, BUt backfire.I put in new fuel filter, cleaned tank, new air filter..I adjusted GAP w/ magnets and coil but have a wek SPark; yellow, faint..ANY way to test the COIL??? and how do I bypass the safety switches or check for bad switch??
I did not pull flywheel off yet..seems a bit complicated..thanks ..any help appreciated..

ANSWER: Hello Again Gail:

Are you Sure the Engine was on TDC? I Rechecked the Clearances and the Valve Specs I Sent you are Correct for this Engine. If the Plug is Firing, then the Coil is Good. Use a Plug to Test the Coil. Holding the Plug Lead to the Engine will Not Test the Coil. It takes a Plug Hooked to the Coil Lead to Test the Coil. If the Plug Fires, then the Coil is Good. Has the Carburetor been Cleaned and the Gas Tank Checked for Trash/Water? From Reading your Description, it Sounds like the Carburetor and the Valves May have Both been Causing the Problem. I have Seen this a Few Times and Usually Once the Valves are Set Correctly, the Carburetor has to be Cleaned to Finish Correcting the Problem of the Power Loss. You have Cured the Backfire and Now you can Cure the Power Loss which Seems to be the Carburetor Jet is Restricted. As for the Flywheel Key; Leave it Alone if the Engine is Not Backfiring. The Runs for a Minute or Less is a Fuel Problem Now. If the Valves were Still Incorrect, then the Backfire would Still be Present. You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.outdoordistributors.com/ and Select the T. Then Select Tecumseh. Then Select Don't have Part Numbers. Then Enter the Model Numbers. Then Select your Model and Download the File for Online Viewing. Since this is a Tecumseh Engine, I have a PDF Site Addy that May Assist you Also. http://www.tecumsehpower.com/CustomerService/BSI.pdf. To Clean the Carburetor,  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 Accidental Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required. If you Can, Please use the Follow Up Option so I can Review our Past Conversations while Reading the New One. Thanks. Here is the Safety Switch Testing Instructions. **PLEASE REMEMBER THAT THE INSTRUCTIONS FOR CHECKING THE SAFETY SWITCHES IS JUST THAT!!! FOR CHECKING ONLY. I NEVER Suggest a Mower be Operated with a Safety Device or Switch Disconnected or Bypassed. Now. On Some Model Mowers you can Simply Unplug the Safety Switch from the Harness. On Other Models you have to Place a Jumper Wire Between the Harness Terminals (on the 4 Post Switch Jumper from Same Color Wire to Same Color Wire). Check the Clutch/Break and the Blade/PTO Safety Switches First. Check the Seat Safety Last. Usually the Seat Safety is Not in the System for Starting the Engine. Just to Ensure Someone is in the Seat when Engaging the Transaxle and/or Blades. PLEASE REMEMBER THAT THE INSTRUCTIONS FOR CHECKING THE SAFETY SWITCHES IS JUST THAT!!! FOR CHECKING ONLY. I NEVER Suggest a Mower be Operated with a Safety Device or Switch Disconnected or Bypassed. Now. On Some Model Mowers you can Simply Unplug the Safety Switch from the Harness. On Other Models you have to Place a Jumper Wire Between the Harness Terminals (on the 4 Post Switch Jumper from Same Color Wire to Same Color Wire). Check the Clutch/Break and the Blade/PTO Safety Switches First. Check the Seat Safety Last. Usually the Seat Safety is Not in the System for Starting the Engine. Just to Ensure Someone is in the Seat when Engaging the Transaxle and/or Blades. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. 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 9pm EST (US). My New Day Starts then. Thanks.

Respectfully

John

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

QUESTION: JOHN!! I finally got his running!! MUrray Riding mower~13 HP Tecumseh engine..  model 40541x99C    OHV130-206810D
Originally it was backfiring like crazy..I adjusted the valves as u said .004 inch for both intake and exhaust..still would not run more than a minute, then would die ..I tested all safety switches..all okay..adjusted coil to magnet air gap;still would not run..I REPLACED IGNITION SWITCH..STARTS UP FINE!! it runs super UNTIL I engage blades, then seems to "hunt..is that the right word? it will rev and then the idle will go lower, then rev again..WHAT is causing this? It happens ONLY when blades are Engaged!
THanks for all your help..I am so HAPPy this starts and runs, but I need this other problem fixed..it did this before I adjusted the valves..and now doing it again! SOS! THANKS, JOHN

ANSWER: Hi Gail:

This is a Common Carburetor Problem. If your Carburetor Model has them; it can be the Air Mixture Screws Require Adjusting or the Carburetor Requires Cleaning. These Instruction should Assist you in Locating and Adjusting the Air Mixture Screws. ****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 the Farthest from 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 the Carburetor Does Not have the Air Mixture Screws, then Follow the Instructions for Cleaning the Carburetor and that Should Correct the RPM Hunting. The Recumseh PDF Site Addy I gave you will Assist in the Carburetor Repairs.Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John

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

QUESTION: Hi John this tractor is hexed I think! Today it would not stay running long at all(less than a minute or so), and yesterday it seemed fine; kept running. My main problem is its stalls after sorta reving up and down, then stalls..THIS is WORSE when I engage the blades to try to mow...As soon as I try to lower the throttle cable to a LOWER speed, it stalls..if I put it all the way up, it runs better, but seems like its misfiring..running rough..hunting.
I already changed: FUEL FILTER, PLUG, IGNITION SWITCH, oil filter,FLUSH OUT GAS TANK(but it has a crack along seam..need new tank, leaking when I fill it to top), ADJUSTED VALVES..I was wondering if the original thought of a sheared fly wheel key would also cause it to do this?????ALSO would the valves I adjusted cause it to run like this ??
I am going to work on carb next as you suggested..IT IS A NON-ADJUSTABLE series 7 type.THANKS
MURRAY RIDING MOWER  13HP TECUMSEH ENGINE  OHV130-206810D
model 40541x99C

Answer
Hi Gail:

The Reving Up and Down (Hunting) will be the Carburetor. If the Gas is Free Flowing to the Carburetor, then the Carburetor Needs Cleaning. The Problem you Described is Usually caused by the Gas Flow Being Slightly Restricted to the Carburetor or the Jet. The Flywheel Key will Usually cause the Backfire or Not Run at All, but Seldom Causes RPM "Hunting". Re-Reading your Last E-Mail and This One Together Tells me the Carburetor is the Most Likely Cause. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John