I have a Snapper mower with a Briggs motor (121Q 02 0028 F1) 850 professional series motor. Withen one year I blew a head gasket on the motor. I took it into my Snapper dealer and had the head gasket replaced under factory warranty. Now when I start up the mower I get White smoke for about 4-5 minutes. Once it's warmed up the smoke dissipates. I'm I looking at another blown head gasket or is there some permanent damage that occurred to the rings/cylinder?