Kohler 321 John Deere 140 runs great when cold, then misses terrible
I am hoping someone will have an idea that I haven't thought of with this tractor. I have a John Deere 140 that I picked up last fall and started fixing it up. I am not a novice at these motors, I have restored at least a dozen of the 110 or 112s, but this is the first 140, and the first time I can remember that I have run into the problem..
The problem: This engines starts and runs perfectly, smooth, no missing, starts right up. When it is still cold, I can slide the throttle to full and the engine will take off and accelerate exactly as it should. If I throw the mower into gear and throttle up, it works perfectly. Then, after about a couple minutes, the engine will start to miss something terrible, loose speed, shakes, and will eventually die. However, if I slide the throttle to idle, it will idle smooth as can be all day with the mower on. I can baby the throttle up slowly and it the rpm will increase to a point smoothly, then the missing starts again something terrible.
I have replaced the carburetor, points and condenser numerous times, new coils a couple times, I have installed a brand new wiring harness, everything works as it should the ammeter shows the battery is charging. The fuel system starting at the tank is flushed, new lines, new filter new strainer in the tank and there is good flow at the carburetor. All parts are genuine Kohler parts. none of these changes have had any effect on the issue.
I am hoping someone else has ran into this problem, because I am stumped. I cant even decide if I have a fuel problem or a ignition problem. Why does it work when it is cold and be so different a couple minutes later? If you can help I would be much obliged to you.