I`m having a big issue with my bike. when the engine warms up and I'm going down the highway it`ll do a little jerk forward and the speed and RPMs will drop quick and even though I have it at full throttle it wont rev up in gear. it sounds like a clutch or carb problem, but I replaced both of those and this problem still wont go away. I`m running out of ideas of why this is happening. any thoughts?