Revvin’ Heaven

Old Bike Australasia - - BLOW YOUR OWN -

Af­ter read­ing the Honda CB72 ar­ti­cle in OBA 49 and then read­ing the “Goofy gears” story in OBA 50, I de­cided to throw in my two bob’s worth. You had to know how to ride them! I was for­tu­nate enough to own a new CB-77 in the ‘60s (reg­is­tered in NSW for $12.00 per year, the same as the 250 cc CB72, due to a gen­er­ous cop­per) and found the gear ra­tios were poorly cal­cu­lated. But then, in the 1960s, most Ja­panese trans­mis­sions were the same, in their cars and trucks. The se­cret was, use the avail­able en­gine revs! CB72s and 77s had a high revving en­gine and by peak­ing the en­gine out to the red-line, a rider could achieve quite good ac­cel­er­a­tion. Th­ese en­gines thrived on RPM. They also had a use­ful amount of torque due to the 180 de­gree crankshaft. I don’t ever re­call hav­ing dif­fi­cul­ties keep­ing up with other (more pow­er­ful) bikes with the CB77. Most of my mates had CB72s and they were cer­tainly not slow in pick-up ei­ther. Later on, I re­stored a cou­ple of CB72s and used a trick to even out the ra­tios by swap­ping the po­si­tion of the 2nd and 3rd gear sets in the trans­mis­sion. This mod­i­fi­ca­tion cer­tainly brought the in­ter­me­di­ate ra­tios closer to­gether ex­cept now, the close step be­tween 3rd and 4th gears be­came a lot wider and the top end pick-up suf­fered.

Apart from the lit­tle trans­mis­sion ra­tio prob­lem, they were a su­perbly built mo­tor­cy­cle with a build qual­ity never again re­peated by Honda. Ball-bear­ing mounted camshafts, roller-bear­ing crankshaft, cen­trifu­gal oil fil­ter, iron “skull” com­bus­tion cham­bers, 180 de­gree crankshaft and mul­ti­po­si­tion footrests. The list goes on. They must have re­ally im­pressed the Laverda fac­tory as they ap­par­ently had a com­plete en­gine sent to them to copy some of the de­sign fea­tures. Hence the sim­i­lar ap­pear­ance. They did not, how­ever, re­pro­duce the 180 de­gree crank and stuck with the “Dream” 360 de­gree style. Rob Rain­bow Dubbo, NSW

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