While we may have sold many engines listed above to be used for a Craftsman YS4500 Mower, Lawn and Garden Tractor Category, we are NOT claiming these are exact replacements unless the product notes explicitly say so. Many original equipment engines may no longer be in production because of obsolescence or EPA regulations, so in some cases there may not be an exact replacement available. Our intention here is to show that other customers have utilized these in the equipment shown, but may have had to make some modifications to do so. If we know of any required changes, we will list those, however, some adapting during installation should be expected.