Resistors (Again)

I'll try to keep it short....9N converted to 12V by a supposedly professional repair business. The tractor starts well and runs OK for a while (anywhere from a couple of minutes to 15 minutes) then runs rough and weak. It might stall if I try to do anything that needs power when it is running rough, but no matter how bad it sounds it will not stall if just left to run on it's own at any speed. (It has a Zenith carb with no place to open to check gas flow, but if I unhook the inlet line gas flows freely and the screen at the inlet is clean.)

I don't know if the coil is 6V or 12V, but there is only 1 resistor in the circuit. It is a ceramic resistor that look like the 8NE10306 that is commonly used in a 6V to 12V conversion. THERE IS NO BALLAST RESISTOR.

1)Is there supposed to be a ballast resistor? (I thought there was supposed to be)

2)If the setup is wrong (too much voltage at the coil) what is the likeliest issue? (points? coil?)

3)Is there anyone in the Mid-Michigan area (Flint) that wants to make a few bucks? I bought the tractor years ago as a hobby and a way to learn a little about engines....I haven't learned and have lost interest and just want it to work!

Thanks

" 1)Is there supposed to be a ballast resistor?"

Yes.

" 2)If the setup is wrong (too much voltage at the coil) what is the likeliest issue? "

The likely issue is too little voltage at the coil.

You can by an adjustable gap spark checker, open it to 1/4" and check spark after it begins to run rough.

Or, skip the troubleshooting and remove the ceramic resistor from the circuit. The tractor should run fine. If it does, then install an OEM ballast resistor. If you have a 12v coil (get an ohmmeter and check if you want to find out) you will have no problems. If it is a 6 volt coil, you will have no problems for a few hours of operation before you over heat the coil.
75 Tips

If you have access to an accurate Amp meter capable of measuring in ten Amp range, check the primary ignition current with the engine not running, ignition switch "ON", points closed.

You are looking for a reading in the 3 to 4 Amp range. If much higher, rapid point failure and coil overheating will occur, if lower, spark will be weak.

If out-of-range, more or less primary resistance is required.

My email is open...I am in Lapeer area...contact me and we can set up a day to look at it...

Tim Daley(MI)