I think the hydro light is for oil temp. I would check the cooler in front of the radiator for being plugged. A worn hydro can build up heat, more heat when going at road speed, or up long hills. If the gap on the electric clutch is too big, it will not pull the clutch disc to the armature, also the brush set screwed into the end of the primary countershaft could be worn and the carbon brushes inside hanging up, tapping on the clutch brings the brushes back into contact.