HY-VO CHAIN
Inverted tooth chains were rarely seen in motorcycle power units until the 1970s. Stronger than a roller chain, especially when wide relative to sprocket diameters. The inverted tooth makes full, positive engagement with the gear-like sprockets. While able to transmit high levels of power and torque efficiently at moderate revs, its weight makes it unsuitable for very high rpm. Carrying the HY-VO trade name, it is sometimes called ‘silent chain’ but can be a source of rattles on the GL1000.
the front crankcase cover casting. Oil is then directed via a pressurerelief valve through passages to the crankshaft bearings, where holes in the big-end shells aligned with holes in the conrods squirt oil onto the cylinder bores. It is also fed to the primary chain, the camshafts and into the hollow gearbox shafts via conduits in caps that close off their front bearings. The smaller rear pump scavenges oil collecting in the clutch compartment and returns it to the sump.
The water pump has an impeller made from synthetic material driven off a slot at the front end of the oil pump shaft. Housed partly in the front crankcase cover and partly in a housing fixed to its front face, it draws via a hose from the base of the radiator to pump coolant through a labyrinth of passages surrounding the bores and combustion chambers. Each head has two removable core plugs behind the camshaft blanking off waterways, and a union on top for a pipe leading to a T-junction, from where water is led forward to a thermostat and a sensor controlling the switch for the electric fan, and then to the upper radiator. It is routed back to the pump through a bypass passage until the thermostat sends it through the radiator at a temperature of 80-84°C.
Twin contact breakers for the coil ignition system are housed, along with a centrifugal advancing mechanism, at the back of the left-side cylinder head, driven by the camshaft.
Thanks to Chris Hunter of the Gold Wing Owners Club of GB for the engine and to 1st Pontefract Scouts for the use of their hall.
‘THE FRONT-RIGHT CARB HAS A CUT-OFF VALVE FOR THE PILOT AIR SYSTEM’