QuestionEngine runs erratically.
I have a McCulloch 32cc brush cutter which has a Zenoah engine.
It started running erratically. It might run good for a few secs, then stops. Restart it and the same thing happens. Some times it will run for a reasonable time (say 20 secs) I have tried a number of things with no success as follows.. The engine has 3 carby adjustment screws, 1 idle speed, 1 slow speed mixture screw, 1 high speed mixture screw.
(1)replaced the carby diaphram, etc with a kit
(2)tried to adjust the fuel mixture but doesn't seem to make any difference
(3)replaced fuel pipes, filter in tank, cleaned fuel system including carby a number of times (makes no difference). Cleaned out with petrol and compressed air. The system looks spotless
(2) replaced the spark plug (spark looks good)
(3) checked exhaust.. no blockage here
(4) compression is good
Any clues?
AnswerHello Len:
>>Are you Sure of the Carburetor Adjustments?
>>Does this Model Use a Point Set or a Solid State Ign Coil/Module?
>>The Following is the Instruction File for Setting the Air Mixture Screws. Any Input is Appreciated. The Procedure is the Same for 1 or 2 Mixture Screws, Just Use the Instruction File and Skip Over the Section with the Missing Mixture Screw ( Usually the H Mixture Screw). Now Setting the Air Mixture Screws: ****Turn the Idle Air (L) and Main Air (H) Mixture Screws In Until SNUG **Do Not Jam** Then Reverse Both Screws 1 1/2 Turns. Set the Throttle Full Open, Start the Engine. Turn the Main Air (H) Mixture Screw Clockwise Until Proper Revs are Obtained. Carefully Use your Finger and Move the Governor Arm to Rev the Engine (on Chainsaws and Trimmers Use the Trigger to Rev the Engine) Until you Reach Max RPMs (on Chainsaws and Trimmers, the RPMs are Not Set to MAX. Set to MAx and then Reverse the Setting Screw 1/4 or 1/2 Turn. If the H Mixture Screw is Set too High; the Engine will be Starved for the Oil in the Gas and Damage the Piston and Jug/Cylinder) and the Engine is Running Proper at Full Throttle Up a Grade. 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 (L) Mixture Screw so there is No Hesitation when Throttling from Idle to Full Throttle. Reset the Engine Idle if Required.****
>>You Checked the Exhaust. How did the Engine react to Running with the Muffler Off?
>>Have you Checked the Flywheel Key? If Slightly Damaged, the Problem you Described can Occur. Some Model have the Key Made as the Flywheel and the Complete Flywheel has to be Replaced. I Once Looked for a Similar Problem on a Chainsaw. The Key had, What Looked like a Scribe Mark on it, but Didn't Look Damaged. Boy was I Ever WRONG. Ended Up 2 Days and I Finally in a Fit of Desperation Replaced the Key. The Engine Fire Up on the Second Pull. I was Some Kind of Red Faced on that One. LOL.
>>Reseal the Jug. Usually the Jug is Sealed with a Special Sealant that you Local Small Engine Repair Center should Carry or at your Local Auto Parts Retailer.
>>The Product is Manufactured by Permatex and is Grey in Color. It is Called Ultra Grey High Torque.
>>If the Jug Seal is a Gasket, then Replace the Gasket.
>>Was the Piston and Cylinder Smooth like Glass when you Cleaned the Exhaust Port and Inspected them?
>>Send me the Model Numbers Off the Unit, Please. With these I can Locate the Proper Manual and Better Assist you.
>>Please, Do Not Hesitate, If you Hit a Snag, if I Missed Something 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. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
