MF 65 runs bad when it gets hot. - HELP

[Toptech]

I am asking for a lot of grace with this post as I am not the owner of the tractor, just the guy trying to figure it out. My BIL has a MF model 65 tractor that runs bad when it gets hot. I looked at the tractor once and this is what I know. It has been converted to 12v, but still uses the generator. I replaced all wiring from the distributor, push button, ignition switch and generator and the regulator with the starter solenoid. There were so many butt connectors on the harness, that it made since to make it with out poor connections. All terminals were replaced at the terminate ends. I ran the tractor and it seemed to run ok, but again is runs like garbage when it got hot. The coil is an internally resistor style coil, so no ballast resistor to the coil. Someone has replaced the points and condenser as well. Fuel does not look restricted, I put a heat shield around the exhaust to rule out fuel vaporization in the bowel. Is there any pointers that I can get from someone that works with these types of tractors?? Thanks in advance.

 

[Powered By IH]

If you shut it off while hot will it restart?
Does the ignition coil fell extremely hot and measure infinite resistance when hot?
If you spray carb cleaner in the intake when it's running poorly does that make any difference?

 

[Toptech]

It seems like it is misfiring when it happens. It does not make any difference if I turn of the ignition and try to restart. I have to travel 1 1/2 hrs to work on this thing and was only concerned with fixing the wiring at that point. The BIL states that if it is cold outside- late fall or winter, It does not do it. I am thinking that it is coil and condenser. The BIL does not know how to operate a DVOM, so I have to guide him on what to do until I get up to him. I am also going to disconnect the generator and see if it is loosing output when hot on the field winding.

 

[used red MN]

It seems like it is misfiring when it happens. It does not make any difference if I turn of the ignition and try to restart. I have to travel 1 1/2 hrs to work on this thing and was only concerned with fixing the wiring at that point. The BIL states that if it is cold outside- late fall or winter, It does not do it. I am thinking that it is coil and condenser. The BIL does not know how to operate a DVOM, so I have to guide him on what to do until I get up to him. I am also going to disconnect the generator and see if it is loosing output when hot on the field winding.

Hello Toptech, welcome to YT. Doesn’t really make any difference but the tractor was probably originally 12 volts. I don’t know what year the one we had was but it was 12 volts. Have the ignition points and spark plugs been looked at or changed? Has the mechanical advance in the distributor been checked to make sure it works and it not locked up? Has a the valve lash been checked (these tractors have mechanical/solid lifters) and a compression test taken?

 

[Jim.ME]

If you don't know when it was last tuned up or by who, it should get a complete tune up (plugs, points, condenser, check of cap, rotor, and plug wires, replace as needed) including checking the valve lash. And timing set by the book. That would be a starting point to me.

 

[miangus]

As mentioned maybe coil. I have had this symptom with a carb issue, if the needle and float do not completely shut off fuel the carb can run rich which is not as much of an issue when cold. When hot the tractor runs but not smoothly.

 

[MKinON]

If it’s only problematic after it’s run a while and is hot, especially since it’s not a problem in cool weather, I’d bet the coil is on its’ way out. Cheap to replace. Have had that happen regularly on an IH140. Don’t know if it’s the tractor or lousy coils, but I always have a spare on the shelf.