Learning to convert
Look strongly at getting a bigger carb for it. If you have a carb with no HS needle, It will be impossible to get it to run right.
On a 25 with the stock carb, stick with a 16-10. It will turn it 7000 to 7100. With the Walbro WA167A from a Zenoah G23, it will do the same with a 18-8.
Enjoy,
Jim