This is my sons mower. The mower would start fine and he would mow 30 to 45 minutes and it would almost bog down and die. He would turn the pto off and idle to park it, it would not take any throttle or it would die. So he checked the spark plugs and said they looked terrible. Changed them out and he mowed the whole yard. Now to the next yard mowing, mowed 30 to 45 minutes and does the same thing as it originally did. Takes a couple of days but he gets it mowed. I told him to bring it out here and let me look at it and ask the experts. He cranked it to load on the trailer and it would only idle, gets here and it cranks and runs fine to where I wanted it parked. It's hard to fix something that isn't broke. Where do you think I should start first. I was thinking about getting on it and start mowing till it messed up here and go from there. Thank for your help.