Hey all, first post here for me, so first off, HOWDY! Heres my dilemma. I picked up this 03 yz250 last friday. Went riding on sunday. Got about 2.5 hours in to our ride, was going on a slight up hill at 1/4 throttle, revs about middle, then brrrrrrrrrrrooohhh POP(with a bit of a "tinggg" sound mixed in. Dunzo. We thought fouled plug, but tried a new plug and no deal. Has spark, its getting fuel, i thought top end, so i took it apart yesterday. There are some vertical scoring marks from near the edges of the skirts, but the rings look good and most of the upper part of the cylinder looks good. Could this top end still be the problem? Big end freeplay is ok, wristpin clips are there, no discernable lower end leaks i can see. Reed valve assy. is good. (havent gotten too far into lower end). I dont have a ton of experience with 2 strokes, so i guess i need opinions on if this is why the bike wont run. Here are a couple photos. Marks in cylinder can barely be felt with your thumbnail. However, the piston's marks seem notably worse. Also, i guess about 20 mins before the no start/no run condition, i thought i had heard some slapping in the top end, but bike was running great, and i didnt think much more about it. Mix was 32:1 with motul 800 2t. Running 50/50 mix of VP ms109 race fuel and premium 91 pump gas. Plug was black but not fouled. I attributed that to it sitting around with the previous owner who didnt ride it very much over the last 1.5 years. Was really puking oil for the first 20 mins, my assumption was the pipe and silencer were loaded up with spooge. It was blowing minimal smoke after that was all cleared out of the system. Any input will be greatly appreciated.