i own a Puch maxi-luxe and i decided one day to clean out my exhuast when i put it back together it sounded like a harley. i haven't fixed it since and ride around and enjoy the laughter i get from people and you should too. Just think when they laugh at you it's because of what you ride, but when you laugh back at them you laugh because they drive a huge car that takes up about 20-40 dollars a week on gas, you also laugh because they alomst always bring there car to a machanic and you can fix your moped in 2 secs. in your own garage.
But for the sound don't worry about it, as long as nothing enters the engine except gas and oil then you will not have any problems.