K90 and K91 are both 4hp K90 is an earlier engine.Production started on the K90 in 1951.
Might be cheaper to buy a whole engine for the parts you need.The little 1959 Wheel Horse suburban 400 I had was all rusted out on the blower housing and the bottom of the hood and the gas tank straps.Rest was decent but the cheapest I could find for a good used blower housing was between $75-100 shipped.
Went to the scrap yard and found 2 complete K91s and 2 in pieces and a K181.Bought all 5 for I think $60.Made the K90 and one of the other 3 run and ended up giving the tractor to a friend for him and his kid to restore.Still have the K181.Saving it for my little cub.
Not to bad if you can get it a little cheaper and have it shipped without that huge hunk of a cast iron Oil sump/generator bracket lol.Recoil doesn't look quite rite but I've seen a bunch with the Tecumseh style recoils.mine had the same one on it.
Edited by EricFromPa, September 25, 2016 - 10:13 PM.