Hey babe. UM to find out if your bikes a 2 stroke just listen to it when it starts up. it should be a high pitch noise. if you cant start it just look at the expansion chamber it should be MUSSIVE! aand the muffler hole shouldnt be bigger than your thumb.RM 125 only come out in 2 strokes any way so it aint a 4 stroke!!! By da way to tell the year there should be a sticker or engraving on the front of the frame(between the shocks) or on the side of the frame in front of the fuel tank. BUT I NEED TO KNOW %!ยค. Like is this bike yours or have you bought for a brother, how old are you. then i will be able to even set the bike up for you or something. SEnd us some pics unfortuenatly my emails fuct up so i cant send you any back. SORRY FOR ANSWERING LATE!!!