Answer to "What do I do if the motorbike does not stay on?"If the bike is carbureted and has been sitting for an extended period of time there is a chance that the float valve is sticking in the closed position. This will prevent fuel from filling up on the carburetor bowl, and starve the engine of gas. I would disassemble the carburetor and give it a good cleaning with a can of carburetor cleaner. A lot of times a dirty carburetor causes similar fueling issues on older motorcycles.