My sister has a 425 with around 800 hours on it. She has had trouble last summer and now this spring again, with it flooding when hot. It starts and runs fine for an hour or so then starts to miss and flood, black smoke. If it stalls it won't start until it cools down. I have not run it and seen this myself. During the winter I couldn't get it hot enough to act up.
Over the winter I installed new plugs, set the valves, lubricated the throttle and choke linkage, changed oil etc.
So thinking out loud.
Would the float stick when hot?
I don't think its dirt or she would have trouble all the time and it wouldn't go away when cooled down.
If its spark related ( the ignition modulator or coil) thats causing it to miss it would smoke black, unburnt fuel.
Any thoughts on this?
I think I will have to run it myself until it acts up see what its really doing.