I have a 1952 Ford 8N that I use for general chores around our small horse farm. When I mow pastures with a 5 foot PTO driven Brush Bull mower I've noticed a consistent decline in how well the engine runs. It will start out running smooth with good power but soon starts to miss and die out, picking up power briefly only to just get so bad it eventually stalls out and won't start. I've finally isolated it to the quality of the ignition points - they are pitted. So when it starts to run rough I'll quit mowing to go file and regap the points to .025 inches. (My manual says .024 to .026.) That seems to cure it for a while. Then I replace them until I have to mow again - so I'm on my 4th or 5th set of points in two years. Other lighter uses with this tractor don't end up like this - I'm assuming it has to do with the amount of power the mower takes. Any ideas? Ignition advance? Carburation? Governor? Thanks in advance (no pun intended).