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Discussion Starter · #1 ·

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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5 Posts

Mo, I have a rhythmic tick coming from the left side of my Grom. It is directly under the access plug for the crankshaft nut. I isolated it using a pseudo mechanics stethoscope (otherwise know as a screwdriver held tightly to my ear) .

I put the motorcycle on a rear stand in neutral so it's definitely not the valves as the motor is not turning over.

I have checked and ruled out sprockets and chain.

While on the rear stand I can slowly rotate the rear wheel until I hear the click. I then move the wheel a fraction (2" either direction) backwards and forwards and the tick is heard with every oscillation.

It sounds as if the crankshaft bearing is notched. I have under 400 miles on the motor, fresh oil and the oil level is spot on.

Any thoughts?
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