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YZ80 head problem among other things

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Ok so got the bits and pieces i needed to try firing this bike up, tried kicking it a few times and nothing. So I took the spark plug out to check for spark, its a brand new plug, and as im kicking it the spark plug hole turns into old faithful. So of course the expletives roll out and now i have to figure out &%$#@! is going on so i take the head off and find one of the O rings is missing about 1/4 of itself.  And looking into the jug I noticed some serious scuffing on the cylinder wall and the piston has a little play side to side even though it looked brand new, barely any combustion marks on it just a little spot of brown. So i take the jug off to inspect further and see that the crankcase is filled to the brim with coolant, but hey on a plus side the crank bearing seems in good shape. So anyway on to the question, i've found 3 cracks on the water jacket side of the head. Will this render the head useless? Post a picture to show location, its really hard to see thanks to crappy cell phone camera but its the line on the little bridge between ports.

 

YZhead.jpg

 

And for kicks a pic of what my cylinder looks like, pistons still on the crank in my shed so i cant get a pic of that. The opposite side looks the same and I can feel some ridges, so now i dont know if i have to bore it out or if it can be smoothed with a bit of fine grit sandpaper. I did not do any of what looks like that in the cylinder already, thats what it looked like when i pulled it apart.

 

YZjug.jpg

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