Small Engines (Lawn Mowers, etc.): White Smoke from Craftsman Lawn Tractor, blown head gasket, craftsman lawn tractor

Question
My Craftsman Lawn Tractor is 2 years old and has lost some power (it has been getting stuck on an incline recently).  Last week, it emitted a great deal of white smoke when I was mowing on an incline.  I had Sears Service come out and they said it was normal and added some oil (I had changed the oil/filter/air filter 3 weeks ago).

Now, after 20 minutes the mower emits enough white smoke to fill my backyard. I notice it happened when I was NOT on an incline.  The first time it was going through a thick patch of grass, the second time, nothing special but a TON of smoke.  I've stopped using it and will have Sears back out.

Since Sears claimed it was normal last time, I'm concerned with what their response will be this time.  Right before the smoke came out, you could hear the engine losing power.

Are there common reasons for this?  How dangerous is this?  Do I need to get this mower completely replaced.

Sears Model: 917.273764
18 HP B&G engine

Appreciate any help!

Answer
 Hello Craftsman Owner:

 The Smoke could be The Crankcase Vent Sticking and Allowing Pressure to Build up Inside the Crankcase Forcing the Oil to be Pushed into the Exhaust Port or by the Rings into the Compression Chamber. A Blown Head Gasket causes the Same Problem. I answered a Similar Question a few Weeks Ago and it was the Head Gasket Blown Between the Cylinder and the Valves. The Engine Power Loss is an Indicator of the Vent and the Head Gasket. Im Thinking Head Gasket. Hope this Helps. Let me know what Happens, Please.

 Good Luck

 Respectfully

 John