Piston/Kickstarter Problem

i have a yz125, just finally got it out of the shop saturday, new crank bearings. i was riding today, and i already knew the carb needed to be adjusted, however, while riding it just stopped. weird? yeah. some smoke was coming out of the exhaust tip. i figured it was oil in the exhaust. but after it would not start. i kicked it over, but its very hard. i do not think its seased up because i wouldnt not beable to turn it over at all. i figured it could have been hydrolocked. so i went back to my house, took off the spark plug, its fine. still hard to kick. took off the head. still hard to kick. no knicks or any discoloration of the piston or sidewalls. so im stuck.
Sounds like a main bearing to me. It could have been put backwards and not getting in oil and you caught it before it seized. Like NUT said pull the clyinder and see if the crank is spinning free and go from there.