All 2st Can't ignore this.....can I ?

2011 WR250 Con rod small end. Looks like corrosion. I've never been through water deep enough to suck any in. Just replacing piston and noticed this, no nasty noises or anything untoward so a bit of a suprise. Anyone else had this. Guess it's got to be replaced.

Yeah maybe. The finish is very similar to the finish on parts of the con rod that have not been machined. Almost like it could have been over size before being machined. But surely that would have been picked up by quailty control.

that's exactly what it looks like to me. a manufacturing defect. if it's worked for 5 years now, I would keep using it. but that's just me being cheap.

You sure that's not heat annealing caused by a stuck needle in the bearing race? I could see it scraping away (causing infusion of bearing material into the seat) at the material on bottom of the seat during the up stroke where there is more pressure due to compression. I'd measure the inner diameter of the seat to be sure it is round.

No you cannot ignore that, its caused by the bike being sat the fuel vapors are actually corrosive and condensation can cause the pitting pictured.
My bottom end looked identical and it was fubared!

So my advise is over winter start your bike and warm her up atleast once a month more the better.

I'm going to borrow some tools from work tommorrow and have a measure. Also will inspect bearing a bit more thoroughly. Gonna replace it anyway but just out of curiosity.

This was a thought I had as well. It only gets ridden about 10 times a year. It has sat for 8 weeks before without being started. I do usually start it if it hasn't been ridden for a while, but on a couple of occasions I left it alone. Maybe a fortnightly start up is in order in future.

It doesn't matter whether it's manufacturing defect, corrosion or just wear and tear you can't ignore it!!
If it's wear or corrosion there's a good chance the big end will also exhibit the same thing. I can't see a manufacturing defect lasting 5years with no ill effects. My bet is its just worn out.
Unfortunately mate your up for a conrod kit and main bearings.

What kind of premix are you using? Thats definetly corrosion not a defect.

The bikes only done 950 miles, so I don't think its worn out through use, but yeah, I know its got to be replaced. I think as stated above, it could be from when it has sat without being started. Will get the Mains and big end checked when its off, probly worth doing anyway while its in bits.

40:1 Castrol racing 2T

Use castrol through out on all my bikes.

Is that oil full synthetic? I have had bad luck with corrosion on motors that sit too long while using full synthetic oil.

wow, that really does look like the rough cast parts of the rod...unreal! i would be glad it hasnt destroyed anything yet and replace it for sure.

It's likely from pump gas and not a defect or the blame of any certain brand of mix oil. Most pump gas breaks down in 90 days and if you introduce ethanol and some moisture it's probably closer to 30 days. Race fuel or AV100 will save you money in the long run

Here's another photo that shows just how similar the area in question is to the un-machined parts of the rod. Corrosion usually leaves a mark where the needle rollers were. There is absolutly no vertical 'play' with the bearing and pin fitted, which is probly why it didn't self destruct and the pin rotates freely with no roughness, bearing itself looks perfect. Havn't measured it yet. I'm starting to think this maybe manufacture error, reguardless, its going to be replaced.

Strange that you say its manufacturing issue, even stranger is my big end on con rod was exactly the same corrosion and yes it makes sence that its corroded where the trapped fuel drips to the lowest point so the tops and halfway up will be dry after a day standing still.

Not arguing just showing you my logic behind the therory.
P.s. Seen it on many old barn find bikes and unless they all used the same conrod manufacturer then its corrosion not manufacturing issue.

No, my comment hints on being undecided. I'm not dismissing corrosion from the bike standing. Its never happened on previous two strokes I've owned in similar circumstances. I've seen plenty of corroded bearings and bearing surfaces before, but in those there was at least a small ammount of roughness on rotation or play. This rotates like a new one. My logic also says corrosion, its just that this does'nt tick all the boxes for corrosion so I'm employing a bit of lateral thinking, but all comments welcome.

Turns out you right. The con rod bearing surfaces are coated, like your cylinder. According to my local long standing husqvarna dealer (who has the engine), this coating has come off in the area of high stress.