I have owned the Scotts 1642 Lawn Tractor about nine years now. Build quality is okay for a low end product. Overall, the only problem I have had with this tractor has been externally with the transmission. Model K51A.
I have replaced the drive pulley and fan three times now. This can be a real time consumer for the do-it-yourselfer. Now I have a stripped shaft atop the transmission. Not wanting to do a rebuild myself, or buy a new transmission for a tractor this old.
I finally welded the pulley to the stripped shaft. It works fine for now, but my thoughts are that I would not recommend buying this tractor. For a little more money, and dropping prices across the various manufacturers, I would shop around.