Sand....
That's a good question. Although I see this is an older thread, I just wanted to point out, after removing my head to my 787, there was quite a bit of beach sand that settled in the bottom of the jugs........for the most part, it didnt' look bad. But for those of you who ride close to the beach regularly, picking up sand, I think you'll be putting more sand in around your jugs. If it gets bad, you'll start insulating the heat transfer through the cylinder into the water jacket.
For the most part, I don't think it's a reason for everyone to pop off there engine heads, but I thought it worthy enough to post.........:cheers: