Outdoor Power Equipment and Small Engines - Advice: Craftsman mower leaking oil

I have a Craftsman 6.0 21" mulit-cut power propelled rotary lawn mower (Model No: 917.377160) that I purchased at Sears around 2000. I know it's a Briggs and Strattan engine and was working fun last fall.

I have mowed twice this year and each time about 15 minutes into mowing oil starts leaking from somewhere at the base of the engine and gets all over the chassy the mower sits on.

When not leaking it runs pretty well so just wondering if I should take it in to have it repaired at $60/hr or is it just not worth it and go get a new mower?

Found a picture on the web: http://newhaven.craigslist.org/tls/150782184.html

Thanks for any advice in advance.

If you know that the oil is not overfilled and that you are using SAE 30 oil, then you need to be more specific as to approximately where the oil is leaking from...carburetor side, muffler side, spark plug side, etc. Areas that it may be coming from are: Oil fill tube seal; Base gasket; Or, the breather assembly based on the fact that it is apparently on top of the deck.

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