After a ten year storage, I had a stuck carburator. Remove the carburator and soak in carburator cleaner. Remove the screw from the top cover. Using a hard plastic or wooden tip and operating through the inlet side of the carburator, pry the cylinder loose. You may be able to loosen it by just removing the air cleaner, spraying in the cleaner while jiggling the accelerator. I had to disassemble mine completely since it was coated with a kind of varnish. This varnish often builds up in two cycle engines. I recommend a complete disassembly and thorough cleaning.
What is the year and model of your Puch. I am looking for an operators manual and a service manual for my 1980 Puch "Newport II"
Good luck, Ken