I just acquired a John Deere 400; and it has relatively low hours. Actually the mower deck looks almost new; as the machine had a snow blade on it, when I got it. Even at that it had not been used in long time.
Tractor look good and runs good; until you try to mow with it. To rule out the mower deck, I installed another 60" mower that I used on another JD 400.
Somebody had been working on this problem and obviously, could not fix it.
Problem: K-532 runs at idle fine, actually a very quiet engine, for a K series. But when you mow and come to an area with heavier grass, and the governor should kick in; it just doesn't run right. It seems to bog down.
New coil and tested good too, new spark plugs, new point to .020", plug wires good. New ethanol Free gas. Compression good. It did have a bad coil and one bad spark plugs wire (completely open) when I bought it. So it was running on one cylinder. Previous owner obviously didn't diagnose the problem correctly and started messing with the governor. You can see the finger prints and dust wiped clean on the parts they touched. So something is messed up now.
Somebody has been adjusting the governor to carburetor linkage. They have not gotten into the governor (still dust on the governor bolts).
I checked all the Kohler manuals, and nothing is printed on how to adjust the above mentioned rod. I did take a rod off of another know good engine to try, it didn't make it any different. I will say the replacement rod was 3/8 of an inch shorter.
Carb is set to specs, air filer is clean; but it seems to go rich when the governor kicks in.
I feel this is the reason for the low hours and not being run in years.