Harley won’t go into first gear while the warm engine is running.

Harley doesn’t switch into the first gear while the warm engine is running. Who knows exactly the problem and what did he do about it? Clutch is new (was not the reason) and all oils are fresh. The phenomenon suddenly occurs for two weeks, has not announced. In cold condition it can be switched on. At the start of the journey, too. After a few hundred meters you step like against a wall. It remains in the second gear. I had after a long drive that I even did not go into the second sha It’s a bit annoying to start at the traffic light with the 3rd gear and grinding clutch. No funny noises. All other gears can be switched. Fat Boy 1990 Greeting, Eddy