ive been running the hitech mg645 for a couple months and i have already replaced 2 of them!....i make sure my epa is adjusted so much to were i barely even have breaks!....and i also have made sure i am not pulling the slide on the carb past wide open! idont even let it go wide open!....it doesnt hit the chassis cause i use the rubber grommets!...i dont know but im on my 3rd one,luckily my LHS just swaps them out with no hassle!