Small Engines (Lawn Mowers, etc.): Briggs valve seat, jb weld, center punch

Question
I have a older briggs model 402707 type 0131 on a jd 116h mower.  One of my exhaust valve seats has come out.  Any ideas on how to fix it?

Answer
Yes, replace the engine.  Seriously though you can re-install the seat and then using a center punch and hammer you can peen around the valve seat.  This is the recommended procedure by Briggs.

Peening is an unusual word.  What you are doing is basically squeezing the aluminum around the seat to hold it in place.  Use lots of little "peens" around the seat.

I  have heard guys say that JB Weld works also.  I have tried both techniques but eventually the seats came loose again.

You might also try a local machine shop.  With as many aluminum car engine heads on the road these days a machinist may offer another solution.

Good luck.
Eric