Oily Spark Plug

[Shorter Grass]

Briggs & Stratton 375
Year: 2005
Model: 10D902
Type: 0129 B1

Lawnmower is slightly smokey on start up but recently is has started to run on reduced power and when I took the speakplug out I found it to be wet and dirty. I have cleaned the plug which was in good condition.

What would have caused the plug to be oily and could my valve stem seals or pistion rings be the likely cause?

 

[ILENGINE]

Your answer could be directly related to which version of the 50,000 engines that Briggs made. We really can't help you without a model number from the engine.

 

[tom3]

I like that VW in your avatar. What does the oil in the mower look like when you drain it for an oil change?

 

[Shorter Grass]

Your answer could be directly related to which version of the 50,000 engines that Briggs made. We really can't help you without a model number from the engine.

Details of engine added in my description now.

 

[Shorter Grass]

I like that VW in your avatar. What does the oil in the mower look like when you drain it for an oil change?

1977 Beetle 1200L that is/was my first car and have owned since early 1980's, having bought it from my father.

Lawnmower oil looks black and smells dirty?

 

[ILENGINE]

I think I would be checking head gasket, as well as valve clearances. Possibly a loose valve seat. Could also be an issue with valve lift due to a camshaft lobe issue.

 

[Shorter Grass]

I think I would be checking head gasket, as well as valve clearances. Possibly a loose valve seat. Could also be an issue with valve lift due to a camshaft lobe issue.

I had the head off the engine 3 years ago and replaced the head gasket then. Valves and seats seemed fine at the time.

The loss of power happened too suddenly for it to be camshaft lobe issue.

What should the valve clearances be for my engine?

 

[Scrubcadet10]

From the operators manual, free download at Briggs website.
Valve clearance with valve springs installed and piston 1/4 in.(6 mm) past top dead center (check when engine is cold).See Repair Manual P/N 270962.Intake0.005 – 0.007 in. (0.13 – 0.18 mm)
. . Exhaust.007 – .009 in. (0.18 – 0.23 mm

Results

www.briggsandstratton.com

 

[tom3]

Basic Briggs flathead Kool Bore.. I'd guess the cylinder is shot. New rings might help it but this is getting pretty common these days. The chrome plating on the piston wears and the bare aluminum surfaces rubbing together creates a mess. Hope I'm wrong but you'll have to pull the head and check.

 

[Shorter Grass]

Basic Briggs flathead Kool Bore.. I'd guess the cylinder is shot. New rings might help it but this is getting pretty common these days. The chrome plating on the piston wears and the bare aluminum surfaces rubbing together creates a mess. Hope I'm wrong but you'll have to pull the head and check.

I will take the head off and see what I find