I came across a 12 hp murray not to long ago, and had to replace the soleinod, gas tank, fuel lines and filter. But now that i have the mower running, it has a bad idle. it revs up and down for a while to the point where it just bogs and shuts off. I believe its the carb in need of a rebuild, maybe the jets just clogged. Any other ideas of what it may be? Ive heard of problems with Brigss carbs.