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Discussion Starter · #1 ·
Hello , I have a problem with the mower stated above blowing heaps of white smoke while running.
I have taken the engine apart and checked everything out . The valves were good , not leaking , the valve guides are clean and the followers are a snug fit inside . The cylinder wall was not damaged or any bad grooves in it. The top two rings looked fine. Put them in the cylinder to measure ring end gap and there was only a tiny little gap , .55 of a mm. This engine has not done much work at all. so very clean inside. The breather tube was not blocked, or had any oil in it . The flap on the part that covers the valve section is opening fine . Oil is not coming from the crankcase into the carburetor . The crankcase has not been overfilled , and the mower has not been put on its side . The head is good and true , used a steel right angle ruler to check it , and the head gasket is good. I am just wondering about the oil control ring. How can u tell if the oil control ring is bad. Mine is sitting in the groove well , and does move , so it is not jammed up. I have just run out of ideas why this engine is blowing so much smoke. I have torn down a few Briggs and Stratton 3.5 hp mower engines before , and then reassembled them and they go great , start easy and not blowing any smoke. . I am using 20w 40 motor oil and have used this oil before in Briggs and Stratton engines with no dramas. I must be missing something , but what . Can anyone shed some light on this dilemma ? cheers Clemenco
 

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I have a problem with the mower stated above blowing heaps of white smoke while running.
Most Often White Smoke Means Valve Guide Wear
The engine will use oil if the valve guides are worn or there is too much clearance between the guide and valve stem. This applies to both, intake and exhaust guides.

Valve Guide Wear Causing Oil Consumption

Valve Guide Wear Causing Oil Consumption

Oil consumption can be more of a problem on the intake side because:
  • Constant exposure to engine vacuum.
  • Oil can also be pulled down the exhaust guides, by suction in the exhaust port.
  • The flow of exhaust, past the exhaust guide, creates a venture effect, that can pull oil down the guide.
 

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Discussion Starter · #5 ·
Most Often White Smoke Means Valve Guide Wear
The engine will use oil if the valve guides are worn or there is too much clearance between the guide and valve stem. This applies to both, intake and exhaust guides.

Valve Guide Wear Causing Oil Consumption

Valve Guide Wear Causing Oil Consumption

Oil consumption can be more of a problem on the intake side because:
  • Constant exposure to engine vacuum.
  • Oil can also be pulled down the exhaust guides, by suction in the exhaust port.
  • The flow of exhaust, past the exhaust guide, creates a venture effect, that can pull oil down the guide.
Ok , I was thinking of that , but this engine is still pretty new. , the valve stems are a nice snug fit when inserted .When the engine was first pulled down , there was no build up of deposits around the valve heads , inlet and exhaust . This is the second time I have pulled this engine down now , and still can see nothing wrong .
 

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After running for a while if you pull the head do you see oil wash on the piston?
If so I would scuff up the cyl and try new rings.
 
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