Roy,

I am out of ideas. Pretty clearly something caused those two cylinders to run lean. You might want to contact the Weiand people to see if they have heard of it before. With an open plenum and non adjacent cylinders it's tough to think jetting would be the cause. Those cylinders are consecutive in the firing order, but I can't think of what impact that would have.

I mentioned the cool dry weather because I have seen a bunch of carburated two stroke boat motors burn pistons on days like that, especially in the fall.

Maybe some of the other wise men will have some ideas. If you figure anything out please let us know. Good luck.

Pat