Adjusting engine speer and a Kohler Courage pro 25

I purchased a John Deere G100 mower and brought it home to find that while my JD LA 165 has an engine RPM of 3300 the Kohler is running about 2450. As I investagated further I found that the.orginal motor had been replaced. I am having a hard time figuring out how to speed the engine up. It is a Courage Pro 25. Modle # is SV830S-0013. I would appreciated any input. Thank you.

https://jackssmallengines.com/jacks-parts-lookup/manufacturer/kohler-engine/courage-pro-sv810-840/sv830/sv830-0012-ariens-25-hp-18-6-kw/engine-controls-group-9-32-1-sv710-840 
 
 
I think this is your throttle control mechanism:
 
Spring #38 can be moved on the governor arm , part #5.  Moving it will change RPMs.
 
But back to basic's first, did you adjust the throttle cable with screw #15 to make sure it 's physically opening all the way?

The harder the spring pulls, the higher the WOT RPMs.
 
A stronger spring would obviously pull harder.
 
I'm not sure on your machine (looking at the pic, I don't think so) but on some others, there's a place to bend where the spring attaches.
That would again, (if bent so the spring is tighter) would also raise RPMs.
 
If your really careful and handy, you could shorten your spring slightly (maybe 1/4") and should see higher RPMs.
 
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