The Idea of a stroker crank is to increase the cc's in the cylinder, and along the way it increases the compression ratio. You MUST have a cylinder or head designed to use a stroker or the piston will top out into the head. Also a specific or modified piston Must be used so it will not bottom out on the crank. Stroking is the oldest trick in the book for creating more HP/Torque. And still the best in my opinion.
WK... Be SURE the 80cc kit you get has steel valve seats in the head. MOST do not. You can have some installed if you already have the head for around 50 bucks at a good motorcycle machine shop. I am having a head done right now. They can do a three angle valve set for better sealing at the same time for around 30.00 more.