Desmodromic Lawnmower

Someone or Something which is a complete waste of time and effort.
Referring to Italian motorcycle manufacturer Ducati's "desmodromic" valve system, used on high performance motorcycles, which is vastly complicated and would give no observable benefits if integrated into a lawnmower engine.

David you fucking desmodromic lawnmower, for the fifteenth time, get out of my house!

Nah, fixing that shed is like putting Desmodromic Valves on a mower.