That engine shouldn't be a grand.
Especially if you swap it yourself.
Shot how? Smoking, knocking? I personally wouldn't put much into a kohler engine or buy a new one. If you must buy a new one, that one runs 850-1000 depending on where you get it.
I am going to guess that if it came originally with a 21 go kohler it is a sub $3000 mower, maybe a toro? (Could have it pegged wrong) if so, it is not worth spending that much on and you are better off buying a new mower.
If it is a 21hp single cylinder like I am thinking, it is not a great engine to start off with.
If you love the mower and must keep it, I would reccommend replacing the engine with a Kawasaki, Honda or Subaru/robin engine. Longer lasting, quieter and just a better engine.
.It's smoking burning oil and knocking some. Low power. At the end of last cutting season it was running ok. Not like it used to. I ran it out of oil, when I realized what was going on I shut it down. Got it running again but now you can tell it's not what it used to be. Steering is slowly going out, I assume that's a filter that needs to be cleaned or changed. It's an 07 that's cut a lot of grass. Body and deck are still in pretty good condition.
Thanks for all the replys.