I have an old JD 420 (1950's), 2 cyl, 6 volt system. All I use it for is to bush hog around the barn and lanes and to plow and disk a small garden. This summer it has started dying after using for usually 30-45 minutes. It doesn't always do this, it's very random. It does seem to happen usually after running for some time. Sometimes it dies and I have to re-start and sometimes it will start to die (just like the key was turned off) and if I shove in the clutch it will start running as normal. When it dies completely, it usually will start right back up, one time I had to wait 5 minutes before it re-started. This past weekend I bush hogged on Saturday for 45 minutes and it had ran fine and then started to die. I shoved in the clutch and turned the key off and right back on and it started running OK. I was done bush hogging so I took it to the barn. Sunday I started to disk the garden and after just 10 minutes or so of running and disking it started to die. I did like Saturday and shoved in the clutch and switched the key off an on. I did this several times and for a minutes or so it just set there running, but missing. Finally it began running ok, so once again I took it to the barn. When this first started happening, I thought it might be fuel related. I cleaned the carb and sediment bowl, but didn't see any difference. I'm no mechanic, but would appreciate any thoughts or suggestions you can offer. Thanks