Honda VTR SP1 – First gear partly bounces out..

Hello! Mostly it happens when I stand at the traffic light and switch from Neutral to the first gear. The green “N” in the cockpit goes out, but as soon as load comes on the drive train the gear jumps out. It seems as if the gear doesn’t really snap! It also happens that the gear bounces out when switching down from the second to the first gear. This is above all a very critical story if I have to switch into the first gear in narrow curves and then want to accelerate again. Unfortunately, it’s ugly that although the speed increases, not the drivage and I “fall” in part into the curves. However, if the first course is (right) in it, it doesn’t go out on its own anymore…. These sympthomes have occurred since I changed the chain set and the oil. Is that coincidence? MFG Tobias Herrmann