After mowing with my John Deere 400 for a while, it starts to blow some smoke out of the muffler and runs rough, sometimes will blow fire out of the muffler and then dies. When trying to start it after it dies, it blows smoke and is very hard to start and runs very rough if it restarts.
But, after cooling off completely and when first started for the day, it runs great.
When I bought it, thee muffler was all rusted through and we repaired it by welding the rusted through sections, and I could hear the baffles in the muffler loose inside it. Could this be a reason for this? If not, what else?
I just put a brand new fuel pump on but it was doing this before I did that and still does.