kx 250 problem

[bike_rider250]

so i went to start by bike the other day after the winter break and when i went to start my bike my kick starter would only go down about 1/4 of the way down and get stuck
so i figured my piston my be a little stuck just from being in the same spot for so long so i put some pre-mix oil in my cylinder to try to free it up
but once i did this the same thing happened over again
the next thing i did was tore my top end apart to look at it and see whats going on in there. everything looked fine and i have done top ends before so i know what it looks like and i coulndt see any problems
so onlce the top end was apart i toke my piston in my hand and i pushed it up and down and it wont do a complete full rotation around in my bottom end
and before i take apart my bottom end i was wondering if anyone knows what would be causing this

 

[Cman250]

How old is the KX? Are bearingings all good in the engine? Last time you rode it was there differences in performance?

 

[bike_rider250]

its a 91
and it rode just fine the last time i have never had any problems with it until now
i also drained the oil and there was nothing in it either