I’m surprised resident 2-stroke god hsiadogah hasn’t chimed in on this. Here’s my NT2 anyway:
2-strokes make more power for a given displacement up to around 500cc. As mentioned, this is because they have a power stroke every two strokes, as opposed to one every four for 4-stroke engines.
They also make gains as they do not have complex moving valve trains like 4-strokes do. The valve train of a 4-stroke creates extra friction. In a 2-stroke the valves are nothing more than holes in the cylinder wall, which are “opened” and “closed” by the movement of the piston. Click here for a better explanation. In this regard, they are very simple and less costly engines. However, the valve arrangement is also their weak point. 2-stroke burn fuel less efficiently because more of the air-fuel mixture charge is lost out the exhaust valve. 2-strokes require oil to be mixed into the fuel as they have other lubrication system. This is an added hassle, and the deposits must be cleaned out of the exhaust pipe or they will burn, giving you the infamous smoky 2-stroke.
Unless you want a very small (<100cc) displacement scooter, and desire to become knowledgable on their maintenance, I would avoid them. A 4-stroke 125cc scooter will be (comparatively) low-maintenance and plenty powerful for a 68kg person. Sanyang Dukes and their ilk are plentiful and cheap to own.
As for going out into the hills… let’s face it, scooters are urban machines. They don’t have lots of clearance and they aren’t designed for big leans. You can have fun all right, just don’t have unrealistic expectations. You aren’t going to be blowing the fairings off the big bikes as you go whizzing past.
And although I don’t like the sound of exhaust, I am forced to admit that 2-stroke 150s are the fastest small bikes on the island, period.
Cheers
kamiwaza
Edited:
Some more things:
Yes, 2-strokes have a narrow powerband, which manifests as a “peak”… on more powerful bikes this can be dangerous for the inexperienced. It’s possible to flip bikes when you hit the powerband (not much of a worry with <100cc scooters).
A CVT that is well set up does keep the engine in its powerband.
TC: In modern 600cc four cylinder sports bikes, the redline keeps climbing higher and higher… 15K, 16K, now 17K+… This is mostly achieved through very over-square bores (ie bore is wider than stroke is long). The downside is you lose bottom-end power. Detractors say that this trend means the bikes aren’t very tractable in traffic, though I’m sure Mordeth disagrees.