Anyone know Briggs&Stratton motors?

I quit working on lawnmower engines about 8 years ago. But I would check the exhaust valve clearence, it might be a little to tight. Clearences used to be .010" on intake valve and .012" on exhaust valve, when cold. Check your owners manual to be sure that they didn't change the clearences in the last few years. If there isn't enough clearence , it will start to stay open when it gets good and hot. Also take a look at the spark plug, if it is white or has white build up, you may have some carbon buid up getting broken loose and getting onto the valve seat. If it is a champion spark plug ,Throw it out!! try these things and let me know what happens?? I hate when you call someplace and get the automated phone system, GIVE ME A PERSON TO TALK TO!!! :x