Well, you can get these sized sprockets from a number of locations: pocket bikes, the valve timing mechanisms on 4-stroke motorbikes, electric scooters and photo copiers. Those little rc motorbikes also use the same types of sprockets.

On my car the sprocket on the engine is from the clutch of a pocket bike engine and the other sprocket (the eleven tooth one) is from an electric scooter.

RS43EVOman- what do you mean by a 'real' engine?, a zenoah G230RC? - to tell you the truth I am only 16 and I do not have enough cash to afford an engine like the ones you guys use. If I could afford one then I would buy one, but I have to make use of what I already have. Plus, this engine only cost me $10