Gms engines seem to be fine...lot of bang for the buck ! Good power...Good idle...Good price... Will pull a tower 40 trainer straight ..."UP".. China has been improving the quality of their product's....Before the tune process, let some heat get into the engine. Don't rush it.. Poor cold weather engine ! Nice warm weather engine.. When the break in process is finished The engine will surprise Your flying buddy's..Make sure the carb is fully seated into the engine. I have Os...Saito..Gms..Tower.. engines....The performance & reliability of the Gms is as good the rest. ( No I do not sell them ).. ( No stock either ) LOL.. Good Luck....