641 Hard Starting

[fisheron]

I have a '58 641 with a 6 volt positive ground system. Over the last several weeks it has become more difficult to start. It starts best when cold and has been taking multiple cranking attempts to get started after the tractor has been working and warmed up. I've checked electrical connections and found bad threads on the starter power cable stud and thought this was the source of the problem. We replaced the starter. Today, it would just crank when trying to restart it after the tractor had been working for an hour. However, it started right up when we used a 12 volt battery to jump start it by connecting the 12 volt battery directly to the starter. This seems to indicate I still have bad electrical connections somewhere in the system. I'd appreciate any input from knowledgeable forum users on troubleshooting this problem. Thanks,

 

[old]

Check the spark when your having problems. It needs to be a blue/white in color and jump a 1/4 inch gap or more. If spark is weak when hot check battery cable connections and also feel the coil if it is super hot it maybe going bad. If spark is weak you could also have a condenser going bad

 

[fisheron]

Thanks, Old,

I'll check things out. The coil after running the tractor for a couple hours measured 122 deg F. using the IR temperature gun and it felt pretty warm but not super hot. Does this indicate the coil should be OK?

 

[showcrop]

the easy start on the 12 Volts doesn't mean anything. It starts well just because it turns so fast.

 

[old]

122 maybe a tad hot but not likely to be out of spec since yes a coil will get warm from running due to 2 things. Engine heat and just flat out heat form what it does