macd
Well-Known Member
Dear Larry, actually it's you that's way off-beam.
Judging by the examples you've given, you've a pretty short memory, so you perhaps weren't aware that the first Japanese 4-stroke vertical twin did indeed have a 360 crank, but then it was Meguro's copy of a British BSA twin, so it would have. (Kawasaki later took over Meguro.) Since then, the overwhelming majority have had a 180 degree crank layout.
In their early years Honda used both layouts, but 180 degree was by far the most common, as in the CB450 'Black Bomber', CB72 and CB77. All the later CD and CB series, of which they sold shed-loads in the 70s and 80s, also used 180 cranks.
Kawasaki's EX500 and later derivatives: 180 degree.
Suzuki GS twins beginning with 400 of mid-70s (and even the early, US-only GR650): 180 degree.
Yamaha's first twin, the XS-1/XS-2/XS650, did rumble along on a 360 crank, but they soon wised up. So 180 cranks were used on the TX and later XS 250/360/400 family of the 70s. The Super Tenere was also 180, as was the early TDM. The TDM adopted a 270 from 1996 (as did the TRX).
As you say, the TRX and Triumph America (not that the latter has anything to do with Japanese practice) run an unusual 270 degree crank layout, but this is as much about appealing to American sensibilities raised on Harley V-twins as anything to do with function.
Far from giving "worse balance" a 180 degree parallel twin has perfect primary balance, but a pronounced rocking couple (which tries to pedal the crank ends around in circles inside the crankcases), which is why so many have used counter-rotating balance shafts.
Yes, 180 crank gives irregular firing intervals, but so what? So do all V- and boxer twins.
Apologies to members for using up space on a boating site for such land-locked stuff, but when I'm incorrectly accused of contributing "garbage", I tend to react.
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Judging by the examples you've given, you've a pretty short memory, so you perhaps weren't aware that the first Japanese 4-stroke vertical twin did indeed have a 360 crank, but then it was Meguro's copy of a British BSA twin, so it would have. (Kawasaki later took over Meguro.) Since then, the overwhelming majority have had a 180 degree crank layout.
In their early years Honda used both layouts, but 180 degree was by far the most common, as in the CB450 'Black Bomber', CB72 and CB77. All the later CD and CB series, of which they sold shed-loads in the 70s and 80s, also used 180 cranks.
Kawasaki's EX500 and later derivatives: 180 degree.
Suzuki GS twins beginning with 400 of mid-70s (and even the early, US-only GR650): 180 degree.
Yamaha's first twin, the XS-1/XS-2/XS650, did rumble along on a 360 crank, but they soon wised up. So 180 cranks were used on the TX and later XS 250/360/400 family of the 70s. The Super Tenere was also 180, as was the early TDM. The TDM adopted a 270 from 1996 (as did the TRX).
As you say, the TRX and Triumph America (not that the latter has anything to do with Japanese practice) run an unusual 270 degree crank layout, but this is as much about appealing to American sensibilities raised on Harley V-twins as anything to do with function.
Far from giving "worse balance" a 180 degree parallel twin has perfect primary balance, but a pronounced rocking couple (which tries to pedal the crank ends around in circles inside the crankcases), which is why so many have used counter-rotating balance shafts.
Yes, 180 crank gives irregular firing intervals, but so what? So do all V- and boxer twins.
Apologies to members for using up space on a boating site for such land-locked stuff, but when I'm incorrectly accused of contributing "garbage", I tend to react.
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