HY-VO CHAIN

Classic Bike (UK) - - Classic Workshop -

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’

Car­bu­ret­tors draw air through gauze pan­els in the air­box

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