Hello, I bought a used 50cc Zip 2 timer yesterday, built in 2000 air cooled, and now also brought it to the running. The carburettor float has to be changed because it somehow overflowed. That’s why I made the air filter dry, removed the carburettor and emptied it and also changed the float. With a new spark plug she went on luckily and also ran well in the stand. Then I gave gas in the stand and it stayed on. but she wanted to drive she partly gave gas on her own and had a funny passage ( couldn’t really speed up well) . When I stopped then she went out with the new gas without stuttering. So when I added gas the speed went down. If I turn it on again and give gas again it runs again and does not go out. My guess is that the 17.5 carburetor is to blame. The Zip has no tuning parts and is up to the 17.5 Verga So I would now order an original 12mm Dellorto carburetor and install it. Can it be because of that? But can it also be that I should just let it run longer in the stand? Or is there any other reasons that can be considered for this behavior? At least now it goes on. I would like to thank you now for any help. Dear greetings Small info: The cylinder and piston is new, so it runs with 1:25 mixture to drive in.