What would cause cylinder corrosion?

[kawi rider 13]

I'm getting my first new piston in my 2011 kx250f and the guy that builds my motors said my cylinder has corrosion and I need a new one, I always start my bike up after I wash it and let it heat up and I use a wash plug, the only other way I could think it could get corrosion is that when it's in my garage and my clothes dryer is on it gets real humid in there, so what would cause cylinder corrosion?

[Altune]

Do you mean corrosion in the cylinder or in the water passages ?

corrosion in the cylinder can be caused by condensation and not starting the bike for a while.

Corrosion in the water jackets can be caused by using plain tap water.

Al

[kawi rider 13]

I think it was corrosion in the cylinder I start the bike every week and weekend so I'm not sure how it could corrode that fast

[Joshx221]

Get some pics. Sounds fishy.

[Altune]

Possible water getting into the motor thru the exhaust valves while it sits, or when washing?

??

[KJ790]

It is almost unheard of for nicasil to corrode. Silicon carbide nickel plating (nicasil) is often used in industry used for it's extreme corrosion resistant properties. I would want to see pictures, sounds strange.

[seehogs]

Very common on a lot of older Kaw 2 strokes. Kaw plating may not

 be the same as other bikes? Mostly what I have seen is pitting

on the cylinder coating.

[kawi rider 13]

If I get the cylinder back from him I'll post pics my dad is picking it up this weekend so I'm not sure if we'll get the parts back the mechanic is posey racing he's by far the most we'll know mechanic in our area he's been covered in mxa magazine and he does over 1000 bikes a year so I don't think he would pull any fishy stuff with me

[Joshx221]

Nonetheless its pretty bizarre. Nicasil doesn't really corrode. I'm curious to see the "corrosion" and also what your riding schedule is, ie. once a week or more or less?

[kawi rider 13]

I ride on weekends and start the bike once during the week and let it fully heat up after washing it

[Joshx221]

There should be no corrosion. The only thing I can think of at this point would be a coolant leak causing corrosion, but even at that its a stretch.