Brute 6.5 mower with running problem?

I have a Noma Brute lawn mower purchased a few years ago. This year the mower has started losing power and stalling on the job. It seems to have something to do with the gasget between the breater body and the carb. When the unit is warmed up or hot the power starts to fait. The mower will start with a priming but soon loses power and fails again. I have not replaces the gasget as yet. Is there a good fix for this problem.