Engine stops more quickly after shutoff than before

[GearHead36]

Mower: Cub Cadet Pro Z 100S
Engine: Kohler EZT750. ~385 hrs.

I noticed on my last mow, that when I shut off the engine, it stops more quickly than it did last season. Or even two weeks ago (when I previously mowed). Should I be concerned? Oil is fresh, and level is good.

One change from last season is, during the offseason, I found that the cylinder cooling fins were almost completely clogged with oily dirt. Of course, now they're clean, and I did another valve adjustment, so the engine SHOULD be running much cooler. Frankly, I don't see how it didn't burn up. I checked compression, and both cylinders are good. One is over 150, and the other is over 160. I also inspected the cylinder walls with an endoscope (boroscope?), and I saw cross hatching on both.

So... is this a good sign? Or bad? Anything I should look out for?

 

[Yardman999]

Due to the fins' cleaning (a good thing), the engine is running cooler. So tolerances are likely smaller, which could explain the former "looseness" at shutdown.

However, other driven devices/bearings outside the engine could have gone bad, so check them out.