Lawnboy Cylinder Head Pics

Joined
Dec 8, 2006
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102
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Jacksonville, Fl
Model 10324 with 2 stroke Duraforce engine. Head gasket was leaking. Engine ran fine, only symptoms were a little harder to start and I could hear a wheeze when pulling the starter rope. I rebuilt this engine about 6 years ago and estimate more than 250 hours on it since the rebuild. Fed a regular diet of pump gas and 32:1 Mobil One 2T until I switched to Castrol RS TTS about 2 years ago, also 1 oz of Seafoam/gal. Is the cleanliness of head due to the engine's diet or the result of the gasket leak? Maybe this is normal but I was a little shocked.
 
Joined
Dec 16, 2006
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Port Orange, Florida
Its the oil you were using. Castrol TTS and Mobil 1 Two stroke oil are top notch. I have tore down many two strokes and the oil being used makes a big difference. I have also had excellent cleanliness with Belray and Yamalube 2R. I doubt the head gasket was leaking severe enough to cause the engine to run lean. Especially on the compression side. I crank seal leaking will cause a lean engine condition. You may lose compression, but not cause a lean condition, since its on the combustion end, after ignition is already occurred. Good condition. Keep using the Castrol. Great Oil.
 

Tom_T

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I was more concerned about the lack of carbon. No cleaning was done to the head and I thought it looked freaky clean when I opened it. I expected it to look more like the plug all over. So I can assume this is more normal than not? I was afraid I had fried something as Spasm3 mentioned.
 
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Apr 1, 2010
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Ontario , Canada
Looking at the pattern on the piston it looks like it was leaking in 4 places ? Any scoring on the piston on the exhaust side ? LB/Toro really should have had 6 bolts in those heads , not 4 .
 
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Tom_T

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Nitehawk - The only leak I could detect was on the top side of the engine. On the head, opposite of the dirty side, is what I believe is a smoke trace from the leak. The exhaust port is on the bottom side of the engine. Cylinder wall feels smooth, I am not planning on cracking the case to check the piston. Pattern on the piston is due to the intake ports on the right & left side of the block. SOHC - In my dreams I thought about flat sanding the head down for more compression but then some wisdom kicked in from somewhere. Why I don't know.
 
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Must have been a lot of turbulance of sorts going on , I don't recall ever seeing a pattern so pronounced like that on a 2 stroke piston . May have been more so due to the leak .
 
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Watertown, New York
When I have a head off a small engine that is questionable, I take some fine sandpaper and place it on a flat surface like a pane of glass or a table saw and work the head over it in a figure 8 pattern.
 
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North Carolina
A machine shop might not charge that much to take a few thousandths off and make sure its flat.
 
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Joined
Feb 15, 2003
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Jupiter, Florida
Originally Posted By: nitehawk55
Must have been a lot of turbulance of sorts going on , I don't recall ever seeing a pattern so pronounced like that on a 2 stroke piston . May have been more so due to the leak .
Those are the transfer port locations. The flow cleans the piston at those locations. Very common on dirt bike 2 strokes to see such a pattern.
 
Joined
Apr 25, 2014
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Illinois
From my experience with Mobil One 2T in a Lawn Boy, a ratio of 32:1 is too much oil. In your pictures the top of piston and portion of the head shows excess oil entering through the ports resulting in the burnt oil deposits. A Lawn Boy engine is a low rpm two stroke and the Dursforce is also fitted with needle and ball bearings. Oils like fully synthetic Mobil 2T should be used at a 50:1 ratiio in this engine.
 
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