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To Re-Plate or Not to Re-Plate

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2002 CR250 that I've owned for about 5 years. I've put maybe 20-25 hours on the bike in that time. Previous owner put a Wiseco in it and I've never torn apart the motor until now. Looks like he neglected to drill the piston to lubricate the exhaust bridge. The dark area looked worse at first, but most of it came off with a Scotch Brite pad. The scoring in the cylinder wall above the exhaust bridge is pretty shallow, it won't catch a fingernail. The rest of the cylinder looks clean and has good looking cross hatch.

This is the first time I've done a top end on a bike with a nikasil bore. Is this a situation where its best to replate or being that its not deep scoring it would be fine to replace the piston and go?

 

 

 

IMG_20170325_141655.jpg

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11 hours ago, CRJohnny said:

Hmmm that's a tough one to answer ,only because I can't see any depth in the picture . If it is deep I would replate. 

Thanks for the reply. Its not very deep that's why I'm unsure replating is necessary.

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I ended up having a local shop take a look at it and they felt the defect went through the coating. Its going off to be re-plated.

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Based on how new the cross hatch looks I would have spent $10 to have a shop hone the cylinder and then inspect it. Looks to me like it has very minor smear which is not that uncommon on those cylinders. A 3o second hone job would either clean it up or confirm it was bad. My money says it would have been just fine after honing.

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Interesting thought. I haven't sent it out yet. I may get a second opinion.

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It will take a diamond hone to even do anything to the nikasil coating. Anything else used and it will just deglaze it and not actually cut into the coating. The coating is only about .002 thick so not much room to work with. If it can be felt i would say honing it isnt gonna help much

Edited by trvshonda

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I agree. Ive worked with Eric Gorr for years and for minor seizures that transfer a little aluminum (smear) to the cylinder a standard hone will remove the smear and leave the Nicasil untouched. After that you'll know the condition of the cylinder. Sometimes a little smear feels like a score and this will help clean that up. Its not meant to do anything to the nicasil.

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