KZ200 Metal Gasket Failure

I helped rebuild my friend's KZ200. It was bored out to 1mm oversize and fitted with a larger piston and rings. He's been riding it but I noticed a loud ticking coming from the top end. We ended up taking it apart again and I discovered the metal gasket that seals the top of the cylinder is coming apart. A piece of metal broke off of it and was sitting on top of the piston. It doesn't look like there's any damage other than the gasket being destroyed. My question is, since I used an oversized piston, will I need a larger gasket too? I didn't think the piston would ride high enough to touch and shred that gasket. I got the gasket out of a rebuild kit so I was thinking perhaps I had the wrong one. I ordered a NOS gasket for the model in question. I'm afraid to put it in though without more info. Any help would be appreciated. Where did I go wrong?

Yes a larger gasket is required.

Thanks, Baldy. Anybody know where I can locate one or a part no?

It's a 1978 KZ200A-1

I ended up using a Dremel on the gasket and enlarged the inner diameter. I slipped the gasket over the stock piston and measured the gap with a feeler gauge. I ground the gasket out to match with the oversize piston. So far so good. The bike is back in service now.