Small Engines (Lawn Mowers, etc.): Briggs intake Valve seat, valve seat, chioce

Question
I have a briggs Model 286707 Type 4529-E1
Code990317ZD
I have a problem with the valve seat , it came of once and I talked to a Mec. who said to take a punch and set the seat in place and pene around the seat being carefull not to go into the valve seat area. I did that and it worked. allthough after one season. The valve stuck open on me. I took the head off again , and found that the seat was still ok , but the valve shaft was slightly mard , so I fixed that so it ran in the giude smooth again. Put it back to gether and it ran great for half of the lawn. and it stalled again. I took the head of again and found the same valve seat poped of again. Mabe I did not use the punch correctly? and did the valve shaft get damaged the first time and I was not looking for that? What do you suggest? I was thinking, new valve. And is there any way I can fix that seat , short of bringing it in to have it pressed in? Or is that my only chioce? And will this happen again?
Thanks Tim  

Answer
 Hello Tim:

 If you want to Solve the Problem and Be Sure it wont Bother you again, then Take the Engine to a Shop and have an Oversized Seat Installed. This is the Only way to Properly Repair this Problem. I have used the Pene Cure Before and this Only Last for a Short Time. Replace the Valve Also. The Stem May be Warped Slightly. You can View a Breakdown/IPL of this Engine at this Addy http://shop.briggsandstratton.com/BShopProductListingPage.asp?rsvp=0&PARENTID=0&... and Enter the Model and Type Numbers. On the Next Page Scroll Down to the 2nd Listing and Click on View PDF. Hope this Helps. I am here if you Require more Assistance. Thanks.

 Good Luck

 Respectfully

 John