Need help with stutter!

Hello, I recently just put together my 80cc motorized bike kit(Here is a link if it helps: http://www.amazon.com/gp/product/B00I2KZVVS?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00) I took a nice ride the first day of making it and wasn't able to ride for a little while after. A few more rides and it was fine. Just last weekend I decided to take it for a spin around my street. When I started it I noticed a sputtering or stutter with the engine. Today I tried it after replacing the gas the other day and it still has the problem. I cleaned and drained the corroborator multiple times and check the plug(It has a spark). If anyone has a solution or fix please send it my way! Thank you and have a nice day!