Hi I have a little scooter problem. My wife gave me a Piaggio sfera 50 RST. At the beginning he didn’t run the seller said you just had to clean the carburetor. I made it and also new spark plugs and new battery. He then always jumped well. Recently the following happened. I drove it for the first time properly. I noticed that he only accelerated a little at about 30 kmh. Sometimes it goes down to 40 then again. In addition, he jerks quite. On the return trip it was worse and at some point it went out completely and no longer on. If you have kicked on the kickstarter or the e starter a loud pffff came out of the exhaust sometimes. I then dismantled everything the vacuum valve was defective and I changed. Also the piston was broken and I changed. I then thought construction everything together and well. Unfortunately the problem is still . So that he does not pull, that hardly give gas. In the stand sometimes he can’t push himself because a brake is closed. I also have to fix that somehow. If he stands on the stand and you give gas you hear the sound again pfffff from the exhaust every few seconds. Can someone give me a tip what can be done there? Unfortunately, I’m a total beginner and I’ve already Googled a lot. (Zündfunke is there)