I've owned Honda Acty's for the past 3 years and have loved them. This is everything I've learned in those past 3 years.
If you're looking for speed upgrades, here's the list:
1. Adjust the carb for the altitude you live at. Once I adjusted my first acty for the 5500 ft of elevation I lived at, it had noticeably more power.
2. Get a performance exhaust. Wirrus Win makes a great one.
3. Ditch the air filter cover. It’s kinda like installing a custom cold air intake, just a lot cheaper
4. The stock air filter is trash. Take the time to find a good one
5. Taller tires and rims will increase your top speed. The Acty will fit 14” rims without a lift. While you’ll sacrifice some acceleration your top speed will go up.
6. Turn the AC off! It sucks the life out of this engine.