The Sportster has a clutch problem. First it started sticking and wouldn´t disengage until the engine warmed up. Now it both sticks and once it warms up it slips in 3rd and 4th gears. Also the clutch chatters when cold and sounds like gears are slipping. I have used info. in the manual to adjust the clutch, but that didn´t help. Any ideas why it both grabs and slips? Thanks