http://www.thumpertalk.com/forum/showthread.php?t=700136 Did the white vinegar thing on the used YZ I'm going through. Got 16 oz. of vinegar at the grocery store, dumped it all in on top of a bit of distilled water, then topped it off with distilled water. Ran it until the left-side upper radiator tank that the head discharges against cleared 100F. On the first drain, I noticed that a lot of the plating on the brand new drain bolt seemed to have been stripped where it had contacted the mixture. This is definitely aggressively cleaning. Remember that most sacrificial anti-corrosion coatings (zinc-laden, in particular) are going to have very little resistance to acid attack. My neighbor's BMW brake calipers came with some of the best anti-corrosion coating in the world on them, but the stealership's detailer has destroyed it with acidic wheel cleaners. Might try 1/2 pint of vinegar if I feel a need to do this again.