On my 14 Triglide when I ride on the Interstate 70-75 mph for a while and start to stop the clutch lever is slack,you can barely feel any resisrance.Pump the lever a few times and it gradually comes back.It's been doing this for a while but gotten worse.Strange thing is if I ride it around 50-55 it doesn't do this. It feels like air in the system.Any ideas are appreciated.