Ask MO Anything: Transverse or Longitudinal V-Twin? - Yamaha FJR Forum : Yamaha FJR Owners Forums
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post #1 of 5 (permalink) Old 04-12-2017, 02:09 PM Thread Starter
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Ask MO Anything: Transverse or Longitudinal V-Twin?



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Dear MOby,

Excuse the noob question, but what’s the difference between a transverse V-Twin and a longitudinal one, and what are the advantages of each?

Navigational Ade


Dear Ade,

It has to do with the orientation of the crankshaft. Any engine, be it a V-Twin, V-Four, or inline-Four, is considered to be “transverse” if its crankshaft lies perpendicular to the motorcycle’s wheels, i.e. across the frame, parallel to the axles. Most motorcycles have transversely mounted cranks, including all Harley-Davidson V-Twins, nearly all four-cylinder sportbikes like the Yamaha R1, Kawasaki ZX-10R, Aprilia RSV4, all Ducati V-Twins and V-Fours… including the Monster 797 pictured on the left, above.

Chain or belt drive to the bike’s rear wheel is simplest and lightest with this layout, and having the crankshaft spinning in the same plane as the rear wheel means power can be transferred through the gearbox and straight on into the drive chain and rear sprocket without making any power-sucking changes of direction.
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post #2 of 5 (permalink) Old 04-12-2017, 04:44 PM
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Longitudinal motors are more efficient for shaft drive, like the moto-guzzi, ST1300, Gold Wing and most BMW's as the power only needs to be turned 90 degree's once. A traverse engine, like the FJR has to turn the power 90 degree's twice. Each time you turn power 90 degree's you lose about 9-11 % efficiency due to friction. So an FJR is at a disadvantage compared to a BMW on the order of 10% and to a chain driven or belt driven bike to the order of 15% or more.

07 FJR 38,000 miles 03 Yamaha FJR1300
1986 Yamaha FZX700 1977 Kawasaki KX250 1978? Yamaha TY250 1979 Yamaha YZ250 1970 850 Moto Guzzi 1974? Honda XL 100 1978? Yamaha XT500 1975 Yamaha RD350B 1964 Bridgestone 90S
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post #3 of 5 (permalink) Old 04-12-2017, 08:49 PM
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Agree with Philharmonic...........and I will STILL never own another BMW
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post #4 of 5 (permalink) Old 04-16-2017, 05:03 AM
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Originally Posted by philharmonic View Post
Longitudinal motors are more efficient for shaft drive, like the moto-guzzi, ST1300, Gold Wing and most BMW's as the power only needs to be turned 90 degree's once. A traverse engine, like the FJR has to turn the power 90 degree's twice. Each time you turn power 90 degree's you lose about 9-11 % efficiency due to friction. So an FJR is at a disadvantage compared to a BMW on the order of 10% and to a chain driven or belt driven bike to the order of 15% or more.

what you say is correct......................yet yamama

thought of another clever approach

on their earlier shaft driven 4 cylinders

they actually fired the engine ' backwards '[ clockwise standing kickstand side ].................then only
using one (!) 90 degree turn shaft drive

to the consternation of many a home mechanic doing routine service
turning the engine ' foward ' counterclockwise

as they normally would chain drive

not sayin the FJR does .............................hadnt checked
just sayin they did on prev ' FJ ' models
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post #5 of 5 (permalink) Old 04-16-2017, 10:13 AM
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The Guzzi keeps your knees warm, the BMW keeps your feet warm.

Pick the bike for the season

Steve

2005 Yamaha FJR1300A
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