pitting/holes in cyinder wall

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11/17/2013 6:13 PM

Hey first timer here, just wondering if anyone could tell me if this is ok to use, or should I have it replated? I just bought the bike recently to resell and don't want to sell it if its going to be a problem in the near future for the buyer. its a yz 125 if that helps. Thanks in advance!

11/17/2013 6:44 PM

I am not an expert.

but I don't see ANYTHING for a cross hatch there, and I think I see what looks to be specs from detonation.

2012 CRF250R #946

"Stop being a dipshit, and we'll both be less aggravated" - GuyB

11/17/2013 6:45 PM

Post a better picture

11/17/2013 7:13 PM

This is about as good a pic I can get without removing the cylinder, but I think it tells a better story. it actually looks worse in the pic than to the naked eye, and now that I can see it that clearly I am guessing it needs plated. Am I right? And what could cause this condition, partial seizure, lean condition or just worn out? Its a 95 with less than 40 hours, i would guess.

11/17/2013 7:15 PM

I haven't pulled the cylinder yet so I'm not sure if the rings are still completely intact, but the bike ran good and has good compression. Could a bad lower end bearing cause this condition?

11/17/2013 7:35 PM

I agree with socket. Just looks like detonation marks. I think your good

11/17/2013 8:01 PM

Ok thanks for the replies, guys. Any other input is appreciated as well. I am in the middle of opening a new cycle restoration co. and I won't sell someone a bike I wouldn't trust myself. Its fairly unnoticeable, at first i thought it may have just been a flaw in the casting/plating So I guess my question to anyone else who might reply: would you run this cylinder?

11/17/2013 8:51 PM

There appears to be a small amount of detonation marks at very top ridge, but the dark pits a little lower in the bore under the combustion ring are just porosity pits from the original casting. Those are nothing to worry about, but the lighter specks further down near the transfer ports are too blurry to make out from the photo. I think they are also just porosity pits that are catching the light and shining, but not 100% about that.

From Millennium Technologies website -

Porosity is gas trapped in the base metal aluminum during casting. These “holes” are exposed when the cylinder is machined or subjected to various chemicals in the plating process. The pits are usually small in size, and in good castings few and far between. When kept under acceptable levels, porosity will not adversely affect the performance or longevity of the engine. In fact, it will improve lubrication. The pits will not cause the coating to peel, nor will a ring hook on them. As far as our specifications on porosity, our cylinders carry a lifetime warranty against defects in materials and workmanship. Therefore, through extensive testing we have found that porosity is a cosmetic problem only. In our pursuit to have both cosmetic and functional perfection we do everything possible to remove these pits. In some cases this is not possible, so we release the cylinder only in cases where it will not affect performance

11/17/2013 9:05 PM

That's the exact response I was looking for. It does look more like a machining defect than damage or wear, as I suspected. And down low looks good the porosity is up closer to the head. Thanks, slipdog and other guys

11/17/2013 10:05 PM

If it is really alot better at the base you might want to check the bore at a few heights. The bottom tends to wear a little more which might smooth the pores out a but. Unfortunately excessive wear will create piston slap which will break skirts. It is ok if it is worn evenly as long as it has the proper piston size in it, but when it starts to get a big taper it causes problems.

11/18/2013 10:04 PM

I'll do that, thanks. Its as good a time as any to learn how to measure cylinder wear. I would ask what tool I need and how to do it, but i'm gonna break the mold and google this one on my own :}

11/19/2013 8:06 AM

Cycle Junky wrote:

I'll do that, thanks. Its as good a time as any to learn how to measure cylinder wear. I would ask what tool I need and how to do it, but i'm gonna break the mold and google this one on my own :}

Use a bore gauge and they are not cheap, unless you have a CMM then use that. And yes those are pits from the casting, not from wear, but I always check my cylinder for out of roundness and check the piston for cylinder wall to piston clearance. Measure the piston with a mic at the widest part on the skirt. The piston should come with instructions on wear to measure it and what the clearance should be. That piston looks like a Wiseco which is forged and the clearance would be about .002". Measure the cylinder bore front to back, side to side, both top and bottom.


REC MX, JE Pistons, Rusk Racing, Yoshimura, Enzo Racing, Dubya Wheels, Asterisk, Rocket Performance, TRE MX, CCR Sport, & MMR

11/22/2013 10:41 AM

thanks for the reply moto. I'll be ordering some tools/parts next week and I'll add a bore gauge to that list. seems like it wouldn't be too bad