I own a Honda Eterno bought in 2003 and done 10,000km. I would like to know why doesn't perform like a 150cc motorcycle even though it displaces 150cc. It belts out a tiny 8.3hp similar to any 100cc motorcycle/scooter and then gives an average of 50 to 60km/l fuel consumption similar to what I hear of many 150cc bikes. Why so?

Can it perform better? If yes, what are the necessary modifications I need to do for the same? I want my scooter to have a top speed of 100km/h with better acceleration.

Scooters are basically meant for better tractability at lower speeds and load carrying given their family use. Also the gearing is meant for the same unlike 150cc motorcycles and better fuel efficiency. It is rather difficult to play around with the gearing of scooters. At the most you can tune the carburettor for a slight increase in pick-up.

It is always difficult to advice on a bike/scooter which is not available in Thailand. But if you 150cc scooter is performing not like a 150cc you probably have a breathing and exhaust problem.

Try to check the air-intake of the engine and check the exhaust system, if your scooter is older then 3 years it is likely that you need to repack your end can.

Seen here how to do this article.php/Learn_how_to_repack_your_exhaust