[nothercrash]

So I've got this 129 mower that I really like. It pulls twelve foot logs, plows snow, mows corn, it's a tank... when it RUNS!

I rebuilt the engine last winter, and it ran and mowed well for about 8-10 weeks this spring. Then it started dying under load, when hot, and eventually got so bad it wouldn't run at all. I replaced the carb, points, coil, and head gasket, with a resurface on the block and head, with no change. Finally I tried a new spark plug, and it did the trick immediately. I mowed with it for the past 4 weeks, and it mowed and ran well, not an issue to speak of. This past weekend it was tough to start, and was running sloppy as it warmed up. When it got fully hot, about 15-20 minutes into mowing, it again began dying under load. I tried several new spark plugs, and they helped somewhat, but didn't bring it nearly back to a healthy run. I ran a new wire from the coil to the points, switched out the plug to coil wire, both with no change. I popped out the plugs (tried this with a few of them), and held them against the head while cranking. The spark was always weak, yellow/orange and small. The spark at the points is bright blue as it should be, and the points are correctly gapped.

What other parts of the ignition system do I need to check? Something seems to be working intermittently. It's also strange to me that the new spark plug did the trick the first time, and not the second time...

Any help would be great. Thankyou, Alex