Open the engine up, and see what the problem is. Find the right engineering shop to do the bore find the parts.
Not sure what it is like here and now, in the past when I have had work the machine shop doing the work sorted all the stuff. But that was two decades ago.
Still need to do some other basic things to get it running and riding. Once it works as a whole, I’ll strip the engine and see how much it’s gonna cost for the top end to be sorted.
As @jung and @airhead advise.
Open the engine up, and see what the problem is. Find the right engineering shop to do the bore find the parts.
Not sure what it is like here and now, in the past when I have had work the machine shop doing the work sorted all the stuff. But that was two decades ago.