This maybe a similar problem, but here is my story about my Kubota ZG-124E.
As you can see via the video below, I am having this stuttering problem. It started to happen during the initial cut of 2019. So, in July and August I went all out to give it a badly needed tune up.
A) Got the blades sharpen.
B) Bought 2 new Pulleys and the serpentine belt.
C) Changed Oil and bought new oil filter.
D) Bought new air filter.
E) Bought new fuel pump and fuel filter.
F) Bought 2 new Champion spark plugs.
G) I found out this mower has another belt that was not mentioned in the manual: electric PTO belt. That snapped and got replaced.
H) I even just now switched to non-ethanol gas.
Everything was fine, I had no more stuttering what so ever. Until, my last cut about 3 weeks ago (we had no rain for a long time) it started to act up again. I would be able to cut for 5 minutes or so than it would sputter. So I stop, shut the blades off and wait for it to get back to normal. If I don't stop and do that, it will stall. Or, if I stop and shut the blades off and wait, and turn the blades on prematurely it will shut off.
So, I thought. It had been a month or so since I cleaned the air filter. Man, was that filled up with dirt and debris. I blew it all out and had it looking new and reattached. That seemed to do the trick, as the mower was now lasting longer than 5 minutes. That did not last long, as it sputtered again. Now it does not act up like this when I drive around with roller brush that sweeps the grass into the basket. So I am confused.
I am no mechanic but my guesses are that:
A) The fuel filter or pump is not working?
B) It could be fuel lines as I did not swap them out?
C) A long shot, but, maybe the battery? Because the mower just died on me before I did the tune ups.
D) Its been a couple months, but maybe the mower deck is clumped up and needs power washing?
E) Even though it was never touched or messed with. The lever that gives speed and choke?