I picked up a 98 yz125 on trade not too long ago. Initially it was a little rough on the out side. Guy I got it from had bought it to flip thinking it needed a top end and ended up needing both top and bottom. He had a buddy that works at Honda do it. It supposedly had less than 2 hours on rebuild, it appears to be true from the looks of it but I'm not thinking we need to pull it apart yet to confirm. My issue is when you are beating the hell out of it, it runs great. After I had time to mess with it and actually get to ride it I noticed the drivability blows. Would buck and not want to go unless you had the throttle open. I pulled the plug replaced it, Cleaned carb and went to adjust air/fuel when I noticed it was 1/4 turn from maxed rich. Got it adjusted and it got better but you couldn't calmly drive it or it would cut in and out and ride like shit till you got on the power band. At idle if you snapped the throttle open it would bog pretty horribly.
I pulled it all apart to did a couple hours of looking around and forum reading and cleaned the hell out of everything. Also checked pilot jet size it was 35, From what I found that's normal or damn close to it. I moved the needle clip up one from where it was (its now 2nd notch from the top IIRC). Put it back together and took it for a spin, Initially the throttle snap is much better, It hesitates for a second than revs out fairly well. The crackling bucking is a good bit better much still under a load when you hammer it it takes a second to pick up than its light a light switch and it takes off, The mid range did seem to improve from moving the needle clip position but mid range wasn't my issue. Iv tried to get the idle air perfect and it seems to be in the best of what it can.
I Just went out again and typically when its not warm 3 or 4 kicks would start it or 1 or 2 with choke, now 1 kick no choke it fires perfectly and idles. That I'm happy about, But while driving unless I'm half throttle while crusing it makes that crackling sound and just doesn't feel right, sometimes when I do get it to smooth out, it jumps to like a super smooth quiet sound where it feels like it should. When it does that it usually pulls a little harder for a sec even thought I don't give it more throttle than it stays smooth and niice until I change throttle. I have never owned a 2 stroke before and I know its not supposed to be a street bike kind of ride but it certainly isn't right and I wanted to lay it all out before I start ordering parts for it and someone may have some advice first. I apologize for the long post especially it being my first but I'm losing faith in my ability to figure this one out. Thanks for the help whether positive or negative. Buddy swears it should have some bottom end not a lot but more than having to feather the clutch and rack it out to leave from a stop.