Fine Wood Carvens Bench My Stihl 026 Runs Fine Until Its Under A Load "cutting Wood" And It Wants To Die,I Changed The Plug ?

My stihl 026 runs fine until its under a load "cutting wood" and it wants to die,I changed the plug ? - fine wood carvens bench

the saw is well and good to run at idle, that is the timber, it will die.