QuestionQUESTION: I was using my Yard Machines riding mower tonight and after about 20 minutes of fine mowing, it started smoking.
The smoke was coming out of the exhaust (front bottom metal box-like thing... is that a muffler?).
I immediately shut the mower off. I haven't started it since.
I don't exactly recall the color of the smoke, but I think I would have noticed if it was blue or dark. I didn't associated it with oil smoke. I think it was white smoke.
Nothing else seemed to be a problem with the mower at the time. No odd noises. I'm not sure about engine heat, but I was doing nothing unusual... just a standard mowing. It normally takes 20-25 minutes... I was right at the end of the job.
I removed the spark plug and found it was dry. I did not noticed any oil on it whatsoever.
I am very much a DIY guy... but I haven't gotten into engines too much. At this point I've inspected what I could without using tools.
The oil level was at the lowest acceptable level... oops. I change my oil every season. Did it a few months ago. I guess I should check it more often. But low oil wouldn't be a direct cause, would it?
I noticed the fuel hose was severely cracked right where it goes into the carburetor (that is a carburetor, right?). If I pushed on the hose just a bit, gas would leak out of the cracks.
I obviously need to replace this hose... no problem, I've already drained the tank... just need new hose. I'll get a new fuel filter too.
But could this be the cause of my engine problems? Air getting in the fuel hose or something? Would that cause smoke?
If not, what should I do? I didn't want to start it up again if it would cause (more) damage.
Thanks for any help!
Ion
ANSWER: Hello Ion:
From your Description it Sounds like the Head Gasket May have Blown between the Cylinder and the Push Tube Galley. You can View a Breakdown/IPL of this Unit at this Site Addy, http://www.buymtdonline.com/webapp/wcs/stores/servlet/Home_YardMan_10101_19502_- and Select the Shop Online Parts Look Up. Then Select the Model Tab. Then Select the OEM (MTD) and Enter the Model Numbers. Then Double Click on the Model in the Results Area. Now you can Select the Section of the Unit you Wish to View. The Following is an Instruction File I Made for this Repair. Any Input Concerning the File is Appreciated. Depending on the Engine Model, Usually the Gas in the Crankcase Oil or White Smoke is Caused by the Carburetor Float Needle Valve Not Seating Properly and Allowing the Gas to Flood the Carburetor and Engine. Then the Gas Seeps by the Rings and Enters the Crankcase and Contaminates the Crankcase Oil, a Bad Diaphragm in the Fuel Pump, a Blown Head Gasket between the Cylinder and Push Tube Galley, the Crankcase Vent Stuck/Frozen/Broken or the Carburetor Flooding the Engine. 1- Clean the Carburetor and Replace the Float Needle Valve (and Seat if this Model has One). A- **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) 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 the Carburetor Float Needle is Good, then; 2- Block the Outlet Port and Pull a Vacuum on the Fuel Pump. If it Holds Vacuum, then it is Good. If Not, then the Diaphragm is Busted and the Pump Requires Replacing. If the Fuel Pump is Good, then Check the Crankcase Oil for Gas Contamination. If the Crankcase Oil is Contaminated, then Drain and Refill the Crankcase Oil with Fresh Oil. 3- **If the Mower has a Manual Gas Shut Off Valve: Check the Manual Cut Off Valve and Make Sure it is Cutting Off the Gas Flow to the Carburetor. A- If Not Stopping the Gas Flow, then Replace the Valve. B- If the Mower Does Not have a Manual Cut Off Valve: Install a Manual Cut Off Valve and Turn Off the Gas Flow when the Engine is Not in Use.** 4- If the Valve is Good or has Been Installed, then Remove the Cylinder Head. On the OHV Engines the Head gasket will Blow Between the Cylinder and the Push Tube Galley. This Allow Oil to be Sucked Into the Cylinder from the Crankcase and the Extra Oil is Just Enough to Cause the White Smoke. 5- Check the Crankcase Breather and Make Sure it is Clean and Operating Properly. 6- If the Crankcase Breather Sticks, then Oil is Pulled from the Crankcase into the Carburetor Throat and this Causes the White Smoke. 7- If the Crankcase Oil is Good, then Check the Gas Tank Cap and Ensure it is Venting the Tank. 8- Some of these Mowers have a Pickup Tube. Remove the Pickup Tube and Ensure the Tube Screen/Filter is Clean and the Tank Does Not have Trash in it. 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: I fixed my fuel line this evening, but decided not to try any engine work yet.
I started the motor (first time since seeing initial smoke), drove the mower around for a few minutes, and got no smoke.
I normally use SAE 30 lawn mower engine oil. But this season I used 5w-30 oil because I have a bunch of it. And the engine manual says I can use it... though it is better for cold temperatures.
Could this oil be causing my problems?
Is the engine getting too hot for this oil?
Should I clean off the engine, specifically any cooling components?
Should I just wait until there is more smoke before trying to fix/change anything?
Ion
AnswerHello Ion:
If the Smoke was White, then it was a Crankcase Contaminated Oil Smoke. This Color Smoke comes from the Crankcase Oil being Contaminated with Gas and this Allows the Engine to Run Hotter than Normal. It can take Anywhere from 10 Minutes to 30 Minutes for the White Smoke to Start. Depending on How Contaminated the Crankcase Oil is with Gas will Determine How Long the Engine has to Run before the Smoking Usually Starts. The More Gas in the Crankcase Oil, then Quicker the White Smoke will Start. I Suggest you Remove the Blower Housing and Ensure the Engine Block and Cooling Fins are Clean. Check the Oil before you Start Mowing and Take No Corrective Action Until it Smokes Again. If the Crankcase Oil is Not Contaminated when you Start Mowing and the Engine Starts Smoking within 20 to 25 Minutes Again, then Change the Oil Back to SAE30. If this Does Not Correct the Problem, then Check the Head Gasket. 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
