Actually if the plug is white not with the chocolate Daniel above mentioned and this bike was kitted and has an aftermarket exhaust your first order of business is finding out if there is an air leak. That isn't necessarily a beginner step and I would hope somebody relatively nearby who is good at Puch mopeds would help you. It's always a problem on a bike with a previous owner who has modded the bike. If I say bought a puch from Ken roff I would know it was lovingly put together.
The worst is that there is a air leak that you don't understand yet and I go blasting around and seize an otherwise great engine because of the air leak. When I see a white plug , if it has been run ..it says I AM LEAN. .. AND and if the jetting range is reasonable then it says ..I have an air leak.
Maybe I would pm Ken roff with all that's on the bike and get advice from him.