First time Zero Turn buyer - ZT1 42"

[abarli65]

I purchased a used (55hr) ZT1 at the end of last year's mowing season. It is in good shape, but I did discover some chinks in the armor and looking to figure out the best course of action.

This has the Kohler 7000 22hp.
- It ran super rich and a spark plug/air cleaner change did not completely correct. Improved, but still very rich.
- It ran a tad erratic when warm and at full rpm. more of a sound than a feel, but it goes in and out of running super smooth, like a smooth hum, to a noisy gurgling.
- the hydraulics are whiny.

I purchased a new carb and swapped that out. That completely fixed the richness issue, but it is still going in and out from smooth to rough. This has nothing to do with cutting, but It is more present with blades engaged, but not limited to actual cutting of grass.
When I had the initial startup, it was super rough, but that fixed once I jiggled the choke lever... it snapped into place and completely smoothed out. But once it heated up, that erratic behavior came back. it is slight, but there and does not seem right. I am wondering if these models have a choke issue?

For the hydraulics, there is no drain on these and are considered "non serviceable", but I did see a youtube on siphoning a quart out and re-filling. I have done that once, and the whine was better, but still there. I may do it again after a couple more mows.

I am now up to 60hrs and I do enjoy not being so tired after walking behind a mower for 90 min. But I am hoping I can manage to make this mower work for me for many more hours to come. I would not mind taking this in to a service center for a once over, but I am certain there are some easy tweaks that can get this thing back to "like-new" condition.

Thanks for your time!