I think the reason I was confused about 16 valve is my sister's '89 is 16 valve (it declares that on the trunk lid.) I sorta thought they'd keep it in the newer years.

But I did the front seals on my '86, so I know the '90 is just like this, so 8 valves.

About seizing, I heard that once the engine cools down, it is possible for the piston to become unseized as it shrinks http://brickboard.com/RWD/index.htm?id=978008 (This is certainly the case in my 2 stroke 63cc scooter, which I have seized and was ok after a few minutes.)

The other poster said the engine could be free, but the 'skirt' (?) collapsed, causing major knocking. Do you know what a skirt is? Or he said rod or main bearings, or seized cam. I was trying to determine seized cam by turning it, but the only part that turned was the first lifter, it just flipped around, nothing else I could see through the oil cap moved.

-Nathan