Laverda Crankshaft: 180 Degree or 120 Degree

Looking at the differences between 180-degree triples and 120-degree triples.


| May/June 2013


So what makes a 180-degree triple different than a 120? Timing, as they say, is everything. On a Laverda 180-degree triple, when the center piston is down the outer two are up. Starting with cylinder no. 1, when that cylinder fires the crankshaft rotates 180 degrees and then no. 2 fires, and another 180 degrees later no. 3 fires. The 4-stroke cycle requires two crankshaft rotations for every firing pulse, so no. 1 doesn’t fire for another 360-degree rotation; it’s like a 4-cylinder engine with one cylinder deactivated. This staggered firing gives the 180 its characteristic lumpy idle.  

With crankpins at 120-degree offsets, the number one cylinder fires, then the crank turns 240 degrees and the second cylinder fires, then another 240 degrees and the third cylinder fires, then another 240 degrees and number one fires again; the cycle repeats with no interruption.

The 120-degree triple has a smoother idle than the 180, but it suffers from “rocking couple” generated by the crankshaft spacing. On the 120, no two crank throws are ever in the same position at the same time as on the 180. Further, on a 120 the force exerted by the pistons and rods as they rise and fall in almost stair-step order literally rocks the crankshaft along its longitudinal axis. Modern triples use counterbalance shafts to counter rocking couple. Laverda quelled the forces with engineered rubber mounts. MC 

Read more by Robert Smith covering the Laverda 3CL.





Ride 'Em, Don't Hide 'Em Getaway

Classic Motorcycle Touring and Events.


The latest classic motorcycle events and tours.

LEARN MORE



The sound and the fury: celebrate the machines that changed the world!

Motorcycle Classics JulAug 16Motorcycle Classics is America's premier magazine for collectors and enthusiasts, dreamers and restorers, newcomers and life long motorheads who love the sound and the beauty of classic bikes. Every issue  delivers exciting and evocative articles and photographs of the most brilliant, unusual and popular motorcycles ever made!

Save Even More Money with our RALLY-RATE plan!

Pay now with a credit card and take advantage of our RALLY-RATE automatic renewal savings plan. You save an additional $4.95 and get 6 issues of Motorcycle Classics for only $24.95 (USA only).

Or, Bill Me Later and I'll pay just $29.95 for a one year subscription!




Facebook Pinterest Instagram YouTube Twitter


Copyright 2018, All Rights Reserved
Ogden Publications, Inc., 1503 SW 42nd St., Topeka, Kansas 66609-1265