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Damaged case mating surfaces

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Hello everyone, I haven’t been on here for a while, but I just found a seized 1996 yz125 on the local classifieds for $300 and I bought it, I have already torn the whole bike down and split the cases, I noticed this on my mating surfaces, IMG_0023.JPGIMG_0023.JPGIMG_0023.JPGIMG_0023.JPG

Looks like someone using a screwdriver or chisel to split the cases, it sucks that I figured this out after already scrubbing the $&%# out of the cases and making them look fresh, I believe the reason for failure of the bottom end was a lean condition and I think this is what caused the lean condition, does anyone have some diy suggestions on how to fix this?

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Take them to a welder have them put bead on it then file down to perfection.  I do it all the time cheap fix and better than jbweld crap. 

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I was thinking about using jb weld, haha, i can see that welding is a much better option, so I better just go with that.

 

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remove all the bearings and such and have a machine shop lap(?)(spelling) it on a surface table

 

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7 hours ago, jsantapau said:

remove all the bearings and such and have a machine shop lap(?)(spelling) it on a surface table

 

That's just going to screw up all your end clearances, so don't do that.

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5 hours ago, Bront said:

That's just going to screw up all your end clearances, so don't do that.

buy the looks of the picture he isn't going to need much and if you are paying a machinist to hand lap it you will probably stop spending the money before you fall out of tolerance

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That should be an easy fix with JB weld if you take your time to draw file and then finish the mating surface with a wet stone.

Surface plate with a new sheet of 400 or 600 wet would help make a nice flat surface.

The welding will require a lot more aggressive filing which present more risk of overdoing it.

Using the grey Yamabond #4 should be better than the #5 thin black sealant.

 

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That should be an easy fix with JB weld if you take your time to draw file and then finish the mating surface with a wet stone.

Surface plate with a new sheet of 400 or 600 wet would help make a nice flat surface.

The welding will require a lot more aggressive filing which present more risk of overdoing it.

Using the grey Yamabond #4 should be better than the #5 thin black sealant.

 

Last night I decided to use jb weld instead of having it welded, I am now sanding it flat with 440 grit, I think it will hold just fine because the damage isn’t that bad, I don’t think the damage is bad enough for it to be welded like other people were saying.

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with a second look of the picture is it even at a critical area?   if it is the extreme outside of where the cases are double walled by a motor mount you aren't sealing anything important 

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