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Does this rm85 bore need replated?

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I'm thinking the answer is yes. It's still got cross hatch, though it may be hard to see in the picture. But it looks like it's got some pretty bad scratches on the first picture. I can just barely feel it with my finger, I'm almost positive that's too much. Just want to get some others opinions, does it need replated?? Thanks20181023_162823.jpeg20181023_162653.jpeg

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1 hour ago, Adric123 said:

 

I'm thinking the answer is yes. It's still got cross hatch, though it may be hard to see in the picture. But it looks like it's got some pretty bad scratches on the first picture. I can just barely feel it with my finger, I'm almost positive that's too much. Just want to get some others opinions, does it need replated?? Thanks20181023_162823.jpeg20181023_162653.jpeg

 

It does need to be replated, Power Seal is good as well as others you got to chose from.

What about the bottom end?

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If you want to prevent it from happening again, it would be wise to investigate how the cylinder/piston got damaged in such manner.

 

Such wear is usually typical of running hot/lean,

once the top end is back together, perform a crankcase leak down test to confirm there are no air leaks and, that the left side crank seal is tight.

 

You may also preventatively go 1-2 steps richer on the main jet if you ride at sustained high rpms / in open terrain.

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If you want to prevent it from happening again, it would be wise to investigate how the cylinder/piston got damaged in such manner.
 
Such wear is usually typical of running hot/lean,
once the top end is back together, perform a crankcase leak down test to confirm there are no air leaks and, that the left side crank seal is tight.
 
You may also preventatively go 1-2 steps richer on the main jet if you ride at sustained high rpms / in open terrain.
Thanks, I think the most likely cause would be the owner before me having an old crusty air filter on there, dirt had gotten in the air boot (I've since replaced the filter and cleaned the boot) I didn't see any discoloration, but I also didn't have the piston off to look in the underside of the piston. Thanks1

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It does need to be replated, Power Seal is good as well as others you got to chose from.
What about the bottom end?
I've got another concern I started thinking about after, what if the scratches are too deep for them to just replate it? I've read about the nikasil being so thin that even honing it destroys it, meaning that scratch is probably past the nikasil and into the metal behind it. Could that mean they can't replate it?

Bottom end appears to be good, but my testing and knowledge was very limited. I couldn't feel any up/down play though

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53 minutes ago, Adric123 said:

I think the most likely cause would be the owner before me having an old crusty air filter on there,

Debris ingestion would show scratches about equally spread around the bore,

in this case it is concentrated in line with the exhaust port, the hottest part of the cylinder.

 

This cylinder is no problem for a re-plater, they've seen much much worse.

Edited by mlatour
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Debris ingestion would show scratches about equally spread around the bore,
in this case it is concentrated in line with the exhaust port, the hottest part of the cylinder.
 
This cylinder is no problem for a re-plater, they've seen much much worse.
Huh, hopefully something major didn't cause it then. What'd you say about a crank case leak down test?

What does that mean and how do I do it? Haha thanks

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Here's a sticky how-to thread pinned in the Honda 2-stroke sub-forum:

 

About 25-30$ worth of simple items from a hardware and auto parts stores builds you a nice test fixture.

The general idea is to seal off the engine, slowly pump about 6psi into it and,

observe if it maintains the pressure for at least 20 minutes with no drop at all.

Edited by mlatour
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Here's a sticky how-to thread pinned in the Honda 2-stroke sub-forum:
 
About 25-30$ worth of simple items from a hardware and auto parts stores builds you a nice test fixture.
The general idea is to seal off the engine, slowly pump about 6psi into it and,
observe if the pressure maintains for at least 20 minutes with no drop at all.
Huh, I'd never heard of anything like that, thanks for spreading the knowledge! I'll look into it more after I tackle the issue of replateing and rebuilding the top end. Thank you
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Here is what a yz250f that I bought looked like after sucking a ton of sand, due to the air filter not being on all the way. In fact if you zoom in on the piston picture you can still see sand sitting on the piston.IMG_2138.thumb.JPG.7dc262028e99b37a7bd9397088364597.JPGIMG_2460.thumb.JPG.778a18b030c0d6562f3bba513438cec3.JPG that dirt may be your issue, where is the piston?

 

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Here is what a yz250f that I bought looked like after sucking a ton of sand, due to the air filter not being on all the way. In fact if you zoom in on the piston picture you can still see sand sitting on the piston.IMG_2138.thumb.JPG.7dc262028e99b37a7bd9397088364597.JPGIMG_2460.thumb.JPG.778a18b030c0d6562f3bba513438cec3.JPG that dirt may be your issue, where is the piston?
 
That looks unfortunate. And I forgot to take a picture of the piston but that's about what it looks like, I've got it loosely put back together now (I won't start it obviously) just to keep it clean, so I can't easily get a picture

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Take some 600grit sand paper to those marks see if its just aluminum from piston.  Whats piston look like?

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Take some 600grit sand paper to those marks see if its just aluminum from piston.  Whats piston look like?
I can feel the scratches with my finger, so unless it had aluminum build up and then get scratched, I think it's actually scratches. Piston doesn't look so great, looks about like the other dudes who posted with the 250 that had sand in it

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5 minutes ago, Adric123 said:
11 minutes ago, Motox367 said:
Take some 600grit sand paper to those marks see if its just aluminum from piston.  Whats piston look like?

I can feel the scratches with my finger, so unless it had aluminum build up and then get scratched, I think it's actually scratches. Piston doesn't look so great, looks about like the other dudes who posted with the 250 that had sand in it

Twostrokes show dirt more on intake side of piston and will kill big end rod bearing.  Looks like aluminum build up to me. Can try to sand it off see if plating is still there. Worth a shot bud

Edited by Motox367
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Twostrokes show dirt more on intake side of piston and will kill big end rod bearing.  Looks like aluminum build up to me. Can try to sand it off see if plating is still there. Worth a shot bud
Okay, I'll try it. I don't have any sand paper that high gritt at the moment, but I'll get some. Thanks
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55 minutes ago, Motox367 said:

Take some 600grit sand paper to those marks see if its just aluminum from piston.  Whats piston look like?

I agree that it looks from this end of the internet like aluminum buildup. I think 400 wet or dry wouldn't be too aggressive on nickasil. If the aluminum comes off and there are still scratches, then it will need replating.

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6 minutes ago, treehopper said:

I agree that it looks from this end of the internet like aluminum buildup. I think 400 wet or dry wouldn't be too aggressive on nickasil. If the aluminum comes off and there are still scratches, then it will need replating.

Have to sand your brains off to get threw coating that stuff is tough 

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Have to sand your brains off to get threw coating that stuff is tough 
I think he just means aluminum from the piston, are the oem pistons made from some sort of special aluminum or something? I mean I guess it makes sense if they are

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Take some 600grit sand paper to those marks see if its just aluminum from piston.  Whats piston look like?
Hey wait I just remembered I saw on a video awhile back that said not to use sand paper on bores because it's slightly poreous and that sand can come off and damage pistons. Wouldn't scotch Brite be a better alternative?

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2 hours ago, Adric123 said:
On 10/24/2018 at 8:18 PM, Motox367 said:
Take some 600grit sand paper to those marks see if its just aluminum from piston.  Whats piston look like?

Hey wait I just remembered I saw on a video awhile back that said not to use sand paper on bores because it's slightly poreous and that sand can come off and damage pistons. Wouldn't scotch Brite be a better alternative?

Lol dam videos.  Goodluck with scotch brite 

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