MOPED ARMY

i had that same exact problem with my tomos. It turned out that the reed valve wasnt opening wide enough when i hit the gas. the little prong that keeps it from opening too far was bent, and was keeping it shut. Now, dont go bending your reed valve in half, just make sure its working right. might also be due to the piston expanding in the cylinder, or something related to the eninge heating up after a while