Mower: Ferris IS1500Z
Engine: Kawasaki FH641V-BS33
Approx 2007 with 1400 hrs
Issue: Bogs down and seems to run very rich under load

Hi all,
I’m stumped on this issue with a mower I purchased over the winter. Unfortunately I didn’t test run it long enough to verify there weren’t any issues like the one I’m having. As soon as a load is added (drive is ok until blades are engaged) it starts to bog down and I can smell the fuel as if it’s running very rich. I changed the plugs & coils, cleaned the double barrel carb and the choke is open when it’s supposed to be. It just runs really rich as soon as load is added. It will occasionally give a burst of power (as if the mixture is suddenly correct) for 15-20 seconds every 15 minutes or so. I was able to get the lawn cut, but it was somewhat of a slow pace, and the RPMs were barely at the point where the blades would be moving fast enough to cut. It looks like the guy had put a new carburetor on it, but the control board/governor spring looks a bit worse for wear. The only other thing I can think of is that maybe the jets need replacing. I don’t think there’s any mixture adjustments on this. I’m also not sure what type of governor it is, and that seems to be a possible issue since it’s just not running well under load. Thanks in advance for any thoughts.
Tom

It sounds like you have one cylinder not firing for whatever reason.
 
Thus, the lack of power and smell of excess fuel
(one cylinder dumping out excess fuel while not burning it)
 
I know you threw some parts at it but check for spark at the spark plug.
Remove and ground the plug (or a known good one) at the head.
You may have to do this once the engine is hot (spark possibly failing with heat)
as well.
 
I'd think one plug would be black(sooty)  while the other a normal color.
 
A compression test would be extremely helpful, a "Leak down Test" even better.
 
Pulling one spark plug wire off while running should/may show one cylinder
not contributing to power output.  
 
Re jets, there are jets in the carb which should not need re-jetting.
Un-less the previous owner messed with them, left them out, they should be fine.
You can pull the carb apart and just inspect.  Use the parts diagram to compare to yours.
 
https://jackssmallengines.com/jacks-parts-lookup/manufacturer/kawasaki/4-stroke-engine/fh641v/fh641v-bs33-4-stroke-engine-fh641v/carburetor-2 
 
.
 

Thank you. I’ll give a try on the compression test. I pulled each plug wire off to test each cylinder when I first got it and all seemed good.

A video popped up in my YouTube feed that discussed these screws. I screwed them all the way in and then back them off one full turn each and started adjusting from there backing them out a half each until I was finally able to get it running fairly smooth underload. Seems like I still need to make some adjustments on both the screws and on the control panel/board to set the idle correctly, but it seems like it’s well on its way and at least I know it can and will run smoothly.