i got a 89 250 moto4, it's been smoking really bad for a while. when i was driving it the other day it was working good, spun on pavement for the first time lol. and i was driving along and i heard a weird winding clicky sounds then it shut off and had no compression. i got it home and took off the cam cover and noticed the cam wasn't turning cause the timing chain jumped off the crank again. so i decided to take the top end off. everything looked good until i took of the cylinder, its in good shape a few little grooves but nothing serious but the piston had chunks blown off the skirt. were did the chunks go and how to get them out? and would a 86 225 head fit on my 250 bottom end?

 

Not sure why the called them Moto 4 225s and later Moto 4 250s? My 87 250 Moto 4 had the same 229cc motor as the 225s had. I would say they would fit.