Earlier quoted context omitted.
Are most of those scooters 2-stroke or 4-stroke? At that scale, the efficiency and emissions differences could make a big difference.
They're two-stroke. Small engines in the developing world are typically terrible - very dirty, very noisy ... and also cheap and easy to fix.
Frankly, India's problem can only be fixed by population control. If Sanjay Gandhi hadn't been an idiot and forever poisoned the idea of population control, India would be much better off, especially if we can get the population to around 300M - 500M