Thank you everyone for your advise. I will use glass and a figure 8 to flatten it with 400g sand paper. Anyone know where I can get a good gasket as I bought a set from the Chinese seller green acre mowers on eBay and they don’t even fit.

Mine being a 160cc it has a rod in the centre of the cylinder with the cup of the rod in the crank case. I don’t think the issue is it it bottoming out and being loose.

I set the gap a couple years back.
Do you guys think the issue is a bad gasket and wrong spark plug?