One of the bikes I'm looking into buying has a rekluse clutch with optional perch. What exactly is that. I knows its an auto clutch but on a bike? Do I still have a fully functioning clutch for when I want it? If so does it act like a normal clutch? Are they hard on a tranny? Do I use the clutch (if it has one) to shift? Any downsides? Powerloss? Upsides? I'm lost in this one please guide me.