Melted Exhaust side of piston

[Toothmech]

Hey guys, my buddy was riding his 96 CR 125 this summer on his way in from the dunes and it siezed up on him. After cooling, the piston freed up but no compression to speak of. After tearing it down the other day, we found the piston melted a little on the exhaust side and we found a severe lack of coolant in the engine. Pretty sure what the cause of the burndown was, but not sure how to repair the cylinder. There are a couple of small deposits of melted aluminum near the exhaust ports, and some mild scoring in those areas, but nothing too horrible. Is it possible to just run a ball hone down in there to take off the aluminum and smooth everything up? Or should he not even bother, and just send it to US Chrome? He's looking for a way to get out of this cheap, 'cause he wants to get rid of it anyway. Any input would be great. Thanks-

 

[TimberPig]

Use muriatic acid to remove the smeared on aluminum. Be careful it eats aluminum, so don't get it where you don't want it, and do it in a well ventilated area, as the fumes are toxic. Dab it on with a q tip or brush, let it sit and work for a couple minutes, and rinse it off with water. Repeat until the aluminum is gone. Once it is off, you can check the plating for damage. If the plating only has minor scuffs, a light hone should make it useable. If the damage is more serious, then its off to the plating shop.

 

[Toothmech]

Hey, thanks for the muriatic acid tip, I'll definitely try that. Thing is, I'm not sure exactly where to get it. Is the stuff you're talking about the same concentration as the stuff you buy in the garden center to clean brick on your house? Or do you have to get it from some other supplier? Thanks for your help.

 

[TimberPig]

Yes, it's the same stuff used for etching concrete, cleaning masonry etc. Just wear gloves and be careful using it, as it is strong stuff. Some places also sell lower concentrations used for cleaning humidifers and such, but they will take a little longer to work.

 

[skipn8r]

do it in a well ventilated area

Very well ventilated....

 

[Toothmech]

Hey, I tried the Muriatic acid trick and it worked very well. I was pretty impressed. I always love it when I DON'T have to send a jug off to the plater. It got the majority of the smears off without any real damage to the Nicasil, only one area was too deep to take out with the hone, but it's below the exhaust ports, so it shouldn't affect compression. Started it up today and it ran great. Thanks again for the tip -

 

[TimberPig]

Glad to hear it worked out for you.

I hope that there weren't any underlying issues (air leak mostly) that caused the seizure, because if they haven't been addressed, the fresh top end may not last. I'd keep an eye on it, unless you are positive the issue has been corrected.

 

[Toothmech]

When we pulled the motor apart, we drained the coolant and we didn't even get enough to fill a coffee cup, so I am pretty sure he laid it down too long in the bed of the truck the last weekend we were riding and the coolant drained out the overflow line by the cap. I think it just got too hot from lack of coolant. When I put it back together I made sure to fill the coolant and when we started it up, it seemed to run great, save for a little jettin gissue, but thats another story altogether. Gotta love a Honda though. After all that, 2 kicks, and she fired right up. Thanks again for the tips-
Ben