carb corrosion ?

[mat4]

I have taken my 4 carbs apart and cleaned them replacing any seals and parts that were showing sighns of age. While doing this I noticed that some of the parts inside the main body of the carbs are going chalky mainly the areas where the float valve seat fits and the needle jet carrier. I wondered if there was a cause for this or is it due to age.
Thanks.

[SteveD CB500K0]

It's usually caused by exposure to air. The aluminium oxidises and you get white powder. Normally not much air inside the carbs.

Just rub them down to clean.

[mat4]

Your right about the alloy oxidisation. Aparently the carbs are made af a zink based alloy and it is as if they have somehow reacted with the fuel or additives in the float bowl and gone weak. The outside of the carbs is fine.
Thanks.