Small Engines (Lawn Mowers, etc.): John Deere mod 100 Lawn tractor engine, small engine mechanic, john deere lawn tractor

Question
John,
Please bear with me as I am not a small engine mechanic.
My Old model 100 John Deere lawn tractor that I purchased for my grandson smoked something fierce. I brought it to a small engine mechanic and this is what he said:
This older Briggs and Stratton engine Model 19707 8HP Type 5147 ser#190707 code 76010714 had it's valve seats casted into an aluminum head and yours has come loose and popped out. You will not be able to reseat this seat as it was casted in. You can not use just any verticle engine replacement as this engine was made for john Deere and had it's crankshaft turned down from 1" to approx 3/4" to fit the Deere cone clutch assembly. You will need to either find a old short block,or a cylinder assembly or maybe get another enine and turn it's crank down. Do you think he is accurate in in his diagnosis and if so, where can I locate  an engine cylinder assembly or short block for such an old engine. Thanks loads, there are not many people that I can ask for this type of help!   keith


Answer
 Hello Keith:

 The Part about the Valve Seat being Cast is True. However If the Seats are Loose, you will have Compression Loss and The Engine will Chatter from the Valve Seats Moving During the Operation of the Valve. The Valve Seat Problem Doesnt Explain the Smoking Problem. A Machine Shop Can Mill the Block for New Valve Seats. It is Expensive. If the Engine was Smoking and it wasnt Over Filled with Oil, then a Overhaul should Cure your Problem. Hope this Helps.

 Good Luck

 Respectfully

 John