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need help with top end rebuild!

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alright guys well i blew my top end on my 1995 cr250 about a week ago. it didnt sieze, just lost compression and when i took it apart today the cylinder wall was deeply scored. i know i need a top end and need to do something with the cylinder. when i took it apart though i found a copper ring below the piston kind of stuck in the crank... so its not the piston ring from the current piston.. they were stuck to the piston, and they were not copper but the copper ring looked that size. there is copper flakes everywhere in the engine.. my questions are these:

1) what do you guys recommend doing about the cylinder? the scoring looks too deep to over bore..

2) how do i know if my bottom end is alright?

3) how do i get all the copper flakes out?

this will be my first actual work on this engine. im going to school to be a marine engineer and im very mechanical so i am very competent to  do the work on my own. all and any help is extremely appreciated. the sooner i can get this done the better... im suposed to ship out for 2 months this summer and i dont want to leave the bike sitting in pieces for so long. thanks guys!

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First thing to do is find a repair manual for it. IT IS A MUST HAVE!!!! I found one online for my 93 for $8 and was an adobe download. You're going to need a couple of specific tool. A case splitter and a magneto/flywheel puller.

It's old man. Tear the engine down to every single piece. Inspect and replace as needed. This is going add up the $'s real quick. Be ready for a cylinder and a crank. All new bearing and seals. If you're finding metal pieces inside YOU MUST do a complete tear down. I mean, you could half ass it but seriously, do it right and do it once.

Edited by GustavMiller
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The copper is probably from the thrust washers in the crank. So.. It looks like you will be doing a bottom end, in addition to the top end.  Like Gustav says above, plan on a crank, crank bearings, crank seals, replate the cylinder, mill & machine the head, new piston & rings, and gasket set for the engine. I just went through all of this except I had my crank rebuilt instead of replaced. I ended up about the $800 mark and that included having my case halves welded to repair the hole that a loose piece of piston skirt punched out. 

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damn... alright guys. im going to end up spending more in repairs to this bike than i bought it for and ive only had it for about 3 months... ran great for a while.

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