Just bought a used '04 YZ 250 that was set up for woods that won't run. Appeared to run rich at purchase (lots of smoke out exhaust and wouldn't clean out while accelerating) which owner said was from brand new top end replacement and that he was running a rich ( I think it was16:1) mixture for first tank break in period. Didn't have a compression tester but it seemed similar to other YZ 250's i have had kicked over. Owner stated crank was checked and was within tolerance so nothing was changed except top end. Got bike home and barely able to ride as it would only run or clean out with near wide open throttle then just died on me! Noticed a lot of gas running out of the over flow tubes after trying several different plugs and different throttle positions while kicking over and even tried the choke once which I am sure wasnt a good choice. Decided floats must be stuck so took apart carb and cleaned and inspected with nothing clogged and no residue. Checked float height and was off minimally so adjusted per manual. Had 178 main 50 pilot. Replaced with 175 main and 48 pilot. Air screw was at 2 1/2 turns out and i tried 1 1/2 as well. Air cleaner was clean and not over oiled. Drained gas tank and got fresh 93 octane gas and mixed at 42:1. Plug was very wet tried new one no luck as it would start but then immediately stall. Interesting note is previous owner said he never had to use the choke to start bike even when cold. A lot of splooge out the exhaust from when it was running earlier. Does get good spark and bike will start for about 5-10 sec if I clean the plug but then just dies out. I have no idea where to go from here as I have never had problems with any other two stroke I have owned! Any suggestions would be greatly appreciated!