I have an xs650, bigger oil pump, oil cooler, and remote filter. The Tacho cable is taken off the oil pump, so if the Tacho stops woking, the oil pump may not be working either. As we all know, the XS650 uses roller bearings, so the oil pressure / flow is low compared to engines with plain bearings. Has anyone got any idea what the Maximum and Minimum pressures should be, and does anyone know where I can get a mechanical pressure guage for this range?