1995 YZ 125 rebuild before and after pics

In august I had bought a 1995 YZ 125 for exactly $480. Two days prior I had sold my '05 TTR-125E for $780.

the YZ had a blown top end and he had told me it was because he ran a spark plug that was too long and that was the reason for seizure.

I tore it apart and half of the piston was completely melted, the rings were melted into the piston head however there was no obvious damage done to the topside of the piston.... liar.

I tore the bike as soon as I got it, starting with gas tank, then radiators, then cylinder head - when I pulled it the cylinder was smooth and piston still moved freely within the cylinder.

did some measuring and inspecting and decided to buy a wiseco piston kit with the piston - 54.50mm + new rings and Athena gaskets + exhaust header springs.

I also bought a 600 grit sandstone hone and stuck it in a wireless drill and went to town on the cyilnder, I'm not sure why people always send out their top ends to get honed. it was so easy.

While waiting for slowco to send me their kit I began removing all of the god awful ugly plastics, and began restoring them with a hard surface stripping gel I picked up at walmart. 

also the plug that was in the bike when I got it was the NGK B9EG, which is what I run right now, double liar..

I don't know what else to say, im bad at thumper talk. enjoy the pics.

comments welcome

 

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I would NOT run that cylinder with the plating damaged like that...

12 hours ago, MaybeMe said:

I would NOT run that cylinder with the plating damaged like that...

been running it in August in that condition, there wasn't any physical damage I couldn't feel any bumps on the surface it's just discoloration, not sure what it was but it didn't affect the surface area, and compression is still good, I'm not worried

Just now, Noah-TeamBlue said:

been running it in August in that condition, there wasn't any physical damage I couldn't feel any bumps on the surface it's just discoloration, not sure what it was but it didn't affect the surface area, and compression is still good, I'm not worried

edit: been running it since August in that condition 

I hope you can look back one day and laugh at what you have done.

Working on a filthy bike: CHECK

Honing a Nikasil cylinder: CHECK

Not removing the CHUNK of piston from said cylinder: CHECK

Obtaining poor crosshatch on said cylinder from using an inappropriate hone:CHECK

Still defending your shenanigans after they're pointed out: PRICELESS!

4 hours ago, Noah-TeamBlue said:

been running it in August in that condition, there wasn't any physical damage I couldn't feel any bumps on the surface it's just discoloration, not sure what it was but it didn't affect the surface area, and compression is still good, I'm not worried

edit: been running it since August in that condition 

I’m afraid not. You’ll probably see why next top end. That is where the aluminum melted into the plating and damaged it. It will create hotspots and potentially melt the piston again, fatigue crack the cylinder, or blow the head gasket. I also wouldn’t be surprised if the plating cracks off and a ring snags it. 

Go ahead and run it since it’s already in, bt be prepared to have the cylinder repaired and replated next time.

13 minutes ago, bikedude987 said:

Working on a filthy bike: CHECK

Honing a Nikasil cylinder: CHECK

Not removing the CHUNK of piston from said cylinder: CHECK

Obtaining poor crosshatch on said cylinder from using an inappropriate hone:CHECK

Still defending your shenanigans after they're pointed out: PRICELESS!

I see nothing wrong with the hone. You don’t want to go crazy with it on the plating and damage it, but I would recommend it on a cylinder that’s within spec, but the crosshatches aren’t visible. They help retain oil and lubricate the cylinder, as well as prevent glazing and the rings not seating. I just don’t agree with the damage and chance of melting another piston.

50 minutes ago, bikedude987 said:

Working on a filthy bike: CHECK

Honing a Nikasil cylinder: CHECK

Not removing the CHUNK of piston from said cylinder: CHECK

Obtaining poor crosshatch on said cylinder from using an inappropriate hone:CHECK

Still defending your shenanigans after they're pointed out: PRICELESS!

"defending shenanigans"

not quite sure if you can read but I was just explaining to him why I did what I did, and what caused me to believe it was fine? Never said what I did was the correct way?

get a life. lol.

38 minutes ago, MaybeMe said:

I’m afraid not. You’ll probably see why next top end. That is where the aluminum melted into the plating and damaged it. It will create hotspots and potentially melt the piston again, fatigue crack the cylinder, or blow the head gasket. I also wouldn’t be surprised if the plating cracks off and a ring snags it. 

Go ahead and run it since it’s already in, bt be prepared to have the cylinder repaired and replated next time.

I see nothing wrong with the hone. You don’t want to go crazy with it on the plating and damage it, but I would recommend it on a cylinder that’s within spec, but the crosshatches aren’t visible. They help retain oil and lubricate the cylinder, as well as prevent glazing and the rings not seating. I just don’t agree with the damage and chance of melting another piston.

Definitely makes sense, I just wanted a beater to ride until I leave home for SFAS. 

I'm hoping one more set of pistons, rings and gaskets before i'll need to do any major cylinder repairs.

on TT, guys are just sharing their opinions from their experiences...you'll like some and dislike others. Emotions and pc don't come across well in forums. most people mean well.
It's a tough crowd...You post up your situation, read the options, and choose the solution that fits you. Sometimes you're right and sometimes you're wrong.
You didn't really ask a question in your original post...you were sharing your experience and then asked for comments.
Let us know how many hours you get on this. One more example for the data bank...

19 minutes ago, Noah-TeamBlue said:

Definitely makes sense, I just wanted a beater to ride until I leave home for SFAS. 

I'm hoping one more set of pistons, rings and gaskets before i'll need to do any major cylinder repairs.

I think it’s possible. It’s just not optimal and it could very well let go randomly. You never really know. They have a bad rep, but I would just throw a Namura piston in on the next rebuild if you’re planning to fix it after that one anyways. They’re cheap and you won’t be wasting a good Wiseco.

25 minutes ago, Sofiedog said:

on TT, guys are just sharing their opinions from their experiences...you'll like some and dislike others. Emotions and pc don't come across well in forums. most people mean well.
It's a tough crowd...You post up your situation, read the options, and choose the solution that fits you. Sometimes you're right and sometimes you're wrong.
You didn't really ask a question in your original post...you were sharing your experience and then asked for comments.
Let us know how many hours you get on this. One more example for the data bank...

if u had to guess I would say about 40 hours so far on the rebuild, so far no issues.

i like your style, but you gonna leave that front brake line flappin in the wind? 

2 hours ago, Noah-TeamBlue said:

"defending shenanigans"

not quite sure if you can read but I was just explaining to him why I did what I did, and what caused me to believe it was fine? Never said what I did was the correct way?

get a life. lol.

Jeez, chapped ass much?  You don't like my opinion, move on.  Don't need to be a dick about it.

image showing correct brake like routing:

 

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Hope OP doesn't jump anything significant with that motor.  Otherwise RIP and godspeed.

3 hours ago, markmc2 said:

image showing correct brake like routing:

 

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thanks, I'll have to buy a mount, didn't even realise.

3 hours ago, bikedude987 said:

Jeez, chapped ass much?  You don't like my opinion, move on.  Don't need to be a dick about it.

if you'd like to tell me how I can do a better job next time is love to hear it, however about honing the nikasil plated cylinder. i know that honing it wears it down but this was an extreme budget rebuild, my first too. it was the only coat effective way - and I wanted to just get the crosshatches back. I ride the bike almost every day and try to take care of it, and I read on thumper talk and people say it's fine to use that hone for their cylinders

5 hours ago, MaybeMe said:

I think it’s possible. It’s just not optimal and it could very well let go randomly. You never really know. They have a bad rep, but I would just throw a Namura piston in on the next rebuild if you’re planning to fix it after that one anyways. They’re cheap and you won’t be wasting a good Wiseco.

I tried getting a namura but the kit was $20 more than the wiseco

Fair enough.  In this instance, honing didn't particularly help you.  It appears that you used a standard 3 stone hone which leaves too rough a finish.  Should be a flex hone or ball hone, just enough to restore cross hatch.  The big mistake was not removing the aluminum first, though.  You can tell in your last pic that not only have you still not removed it, but it was preventing the hone from touching the cylinder wall immediately surrounding the aluminum glob.  Some muriatic (pool) acid applied carefully to the stuck on aluminum will dissolve it without touching the Nickasil.  One more thing: you aren't cycling the hone fast enough in and out of the cylinder, the cross hatch lines should be at about a 60* angle with each other, yours are nearly flat.

As for a budget rebuilt, I understand, but that doesn't mean don't use proper techniques.  If you had asked in the first place, you would have gotten good, helpful advice rather than a roasting.

7 minutes ago, bikedude987 said:

Fair enough.  In this instance, honing didn't particularly help you.  It appears that you used a standard 3 stone hone which leaves too rough a finish.  Should be a flex hone or ball hone, just enough to restore cross hatch.  The big mistake was not removing the aluminum first, though.  You can tell in your last pic that not only have you still not removed it, but it was preventing the hone from touching the cylinder wall immediately surrounding the aluminum glob.  Some muriatic (pool) acid applied carefully to the stuck on aluminum will dissolve it without touching the Nickasil.  One more thing: you aren't cycling the hone fast enough in and out of the cylinder, the cross hatch lines should be at about a 60* angle with each other, yours are nearly flat.

As for a budget rebuilt, I understand, but that doesn't mean don't use proper techniques.  If you had asked in the first place, you would have gotten good, helpful advice rather than a roasting.

I didn't even know about the acid, and I went for a second round of honing after that picture was taken cause I did notice that it was too flat so I went really fast a couple of times and it looked better but I didn't want to wear out cylinder walls to fast so I stopped.

I'll have to try these things out on my next rebuild, thanks 

Edited by Noah-TeamBlue

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