Can't tell if my cylinder needs replating

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#1
My 1998 yz125 cylinder looks pretty good but the bottom half seems like it might be low on the nikasil plating. I am not sure though. Can anyone with experience in evaluating this tell me if it needs replating?





 
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#2
I know the two pictures of the bottom are kind of blurry but thats where the minor scoring is. Also, that scoring is on the sides, could that mean the crank rod bearing (not wristpin bearing) is worn out?
 
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#3
You've got to upload them somewhere like www.photobucket.com first. The bottom half of the cylinder usually barely wears at all. That's what you should judge the rest of the cylinder by. To accurately gauge whether or not the cylinder needs to be plated, you need to mic it.
 
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#4
Alright the pics are up. Mine has wear on the bottom half though.. Is a mic a micrometer? or can i use some calipers?

Oh yeah, spectro 100% synthetic is excellent, i have no carbon deposits in my exhaust port! Nothing caked on!
 
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#5
That's not scoring, that's crosshatching. That's what a new cylinder should look like.
 
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#6
Actually, after looking at it again, it looks like theres a tiny bit of horizontal scoring on the intake side on the bottom.
 
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#7
I beat the crap out of this motor for 2 year, also kept it up well, and this is what it looks like :) .
 
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#8
So by a mic do you mean calipers? My brother knows a lot about motors and said it just needs to be honed. I was skeptical but now im starting to think thats all it needs.
 
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#9
Sorry GM,that is what a cylinder looks like when a fool with tools has at it!Like gm said,bottom is a low wear area.Check your clearances with a feeler gauge where the rings ride.An inside micrometer or bore gauge is handy.Other than fools with tools the finish is damn near indestructible,and when it fails it flakes,just like a chrome bumper,go figure!The material behind the plating will move and distort the bore.
 
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#10
2-strokes don't really need to be honed. Calipers don't really work for this measurement because there is a ridge at the top of the cylinder that doesn't wear and stays at the original diameter no matter how worn the rest of the cylinder. You need a set of snap gauges and an outside mic, an outside mic and inside mic, or an outside mic and a dial bore indicator to measure the piston to cylinder wall clearance. If the cylinder tp piston clearance exceeds .004" or the cyilnder wall taper exceeds .002", it's time for a replate. Like Fox said, they're pretty much good until they wear through the plating. You should be ok to toss another piston in there, but it's always good to measure.
 

Rich Rohrich

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#11
76GMC1500 said:
2-strokes don't really need to be honed.
Does your butt ever get sore from all the time you spend out here talking out of your ass?
 
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#13
1.that's crosshatching.(wrong)2.To accurately gauge whether or not the cylinder needs to be plated, you need to mic it.(wrong)3.That's what a new cylinder should look like.(wrong)4. 2-strokes don't really need to be honed.(wrong)5.You need a set of snap gauges and an outside mic(wrong)6.You should be ok to toss another piston in there(GUESS AGAIN!)That is about that!Yz,a wild guess is that bore is screwed up,you need to determine the bore size and or the piston to cylinder clearance,if it is good then have a professional hone it,chamfer the ports and CHECK THE RELIEF ON THE BRIDGING,good luck.
 
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#14
Ok, I see nothing wrong with that cylinder. The only scratches I can see from the pictures appear to be cross-hatching. Cross-hatching like a new cyliner. Snap gauges and an outside mic are the best way to measure piston to cylinder clearances because it eliminates the bias error of the micrometer. I listed all of the other possible tools that would work, but a caliper won't because you can't measure deeper into the cylinder where most of the wear occurs. Visually, I see no reason he can't put a new piston in and reassemble. For honing, cross-hatching does give the piston rings a little something to wear into. It's not really necessary to hold oil like a 4-stroke, though. The most important reason for honing new 2-stroke cylinders at the factory is to fine tune the bore diameter. Instead of saying WRONG all of the time, lets discuss these things. You don't seem to be right all of the time, either, Fox. It seems that some shops hone and some shops don't. I know it's not a very wide demographic, but the 2 Honda dealerships I have been to don't hone. The third party shops all do.
 
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#15
Define cross and you will see what has happened to that jug.Calipers was asked and you have ranted long enough.A $3.00 feeler gauge will work to determine weather what is usable or not.The cylinder glaze is from FLASHING and should be removed.What in the hell difference does a 2t or 4t make?If some shops are idiots you keep going back?