Glad That You Asked. Why Do Harley Davidson Motorcycle Shake More Than Other Brands.

Harley-Davidson uses a common crank pin, meaning that both pistons travel up and down together at the same time. So all the weight is being thrown back and forth causing vibrations and the very particular “proprietary” sound or rumble.

The Twin Cam engine has a chain driven counter balancer creating less vibrations. As far as I know, the only other 45-deg. V-Twin bike to use a common crank pin is the Honda Shadow Ace American edition in an attempt to attract buyers by copying the Harley sound…and vibrations.

16 Responses to “Glad That You Asked. Why Do Harley Davidson Motorcycle Shake More Than Other Brands.”

  1. 1 gabehcuoD May 15th, 2010 at 11:41 pm

    Another great engine is the Yamaha Road Star / Warrior engines… 1600-1800-1900 all single pin cranks….. You can get some great power out of all these motors with some simple mods… Ive had Nigel Patrick do allot of work to one of my 1600 motors and its a monster for only 1600….. on pump gas…. There have been a few people that have documented over 200K miles on a stock motor that has never been torn down…….

    I’m sure someone will pop up and say that there are a ton of Harley’s with over 200K…. I’m not debating that… This is not posted to start something… just for fun………….. 🙂

  2. 2 Seven May 16th, 2010 at 12:49 am

    Just a small correction, there have been many V twins with common crank pins, not just the Honda Shadow Ace and HD’s. Most use a different V angle that helps to reduce vibration (and aid cooling). But nearly all use more than HD’s 45°, generally the larger thee V angle the less vibration. Most V twin makers now have moved over to an offset crank pin design, the larger the offset the less vibration. A classic example is the old Suzuki Intruder which was sold in the US with a much smaller offset just to make it vibrate more for american tastes.

    here is an more scientific article on whys and whatnots of the forces involved.


  3. 3 May 16th, 2010 at 7:59 am

    Classic Indian and Kiwi Indian engines also have a single crankpin along with a 42 degree V. These engines are surprisingly smooth even when we stroke them to 5-1/4″.

  4. 4 LoganSt May 16th, 2010 at 2:16 pm

    There’s no counter balancer in rubber mounted Big Twins. That’s way they have a little more hp than the counter balancer ones.

  5. 5 May 16th, 2010 at 4:02 pm

    Sorry, what??

    Surely a massive majority of V-twins have a single crank-pin because it is mechanically much simpler than running a second journal and a central web to allow the offset, although Ill acknowledge that it hasn’t stopped Suzuki (and Honda on some engines) using such a system, though I’ve no idea why. The only major difference between the Harley (and H-D-derived clone motors) and most others is that it uses a knife and fork arrangement for the conrods allowing the barrels to be directly in line, rather than them sitting side by side, with an offset the width of a the conrod (or conrod and central web in the case of the oddities).

    Very few motors share the Harley’s 45-degree angle between the barrels, as said, but the misconception is that the pistons therefore travel up and down at the same time: they are out of phase by … hang on, let me think … oh yes, forty-five degrees: therefore they will not hit TDC at the same time, unless the pins were 45-degrees apart. You’ll get that with a 360-degree vertical twin, but not a V-twin with a common crankpin … and that’d vibrate like a bastard without balance shafts (Meriden Bonneville) but can be smooth, silky and soulless with a balance shaft (Hinckley Thruxton). As LoganSt points out, the rubber-mounted Twin Cams don’t have a counter balancer.

    The 45-degree angle of the Harley’s vee exists to allow a compact powertrain, and I’d be interested to know if the narrower (and therefore more compact) angle of the Intruder combined with the offset of the crankpins equates to a 45-degree motor – or maybe the offset is the same as the angle of the vee to counter it, so that it does work like a parallel twin: I should look it up really, but you know what? I really don’t care that much.

    And all of the above only counts if the engines are balanced properly rather than built to within tolerances: it’s often said that balance shafts – and rubber-mounts – are a wonderful way of overcoming the vibration inherent in a production-line motor, absorbing the worst of what is otherwise an expensive thing to tune out.

    Interestingly, most developments in this department are for marketing and stylistic purposes. Yamaha’s TRX850 had basically the same engine but a different crank to their TDM850, using a 270-degree offset to make it ‘fire like a Ducati – they could have just as easily said like a Bonneville – and the sheer number of these bikes you see on the street reflect what an overwhelming success it was at converting Ducati owners to parallel twins. Harley could infinitely rebore their V-twin if they used a 90-degree angle without fear of piston clash at BDC, and they could even offset the crank so it fired like a 45-degree v-twin, and I suspect it would meet with the same success. One day we’ll work out which is the most important thing about Harleys to their owners: the look, the feel, the engineering or the lifestyle that accompanies it. I’m guessing that Honda thought it was ‘the feel’ with their American Classic Edition, but I’m guessing they overestimated how much.

    I’m just mystified why Triumph bothered to fit a 360-degree crank into their Thruxton and then balanced it well that it might just as well be an electric motor … although it does sound authentic … or would if you could hear it.

  6. 6 May 17th, 2010 at 3:51 am

    And I personally like that style of Harley engines. Vibrations… I don’t care/ I’m not a small girl, who want my bike be calm, “green” and extremely convenient.

  7. 7 grayhawk May 17th, 2010 at 7:39 am

    Guess if the bit of vibration is too much for ya you can put a snake in the handlebars as of old or bring back the Sputhe 60 deg version of their vtwin motor, if memory serves me;

    or Cyril can do an a blog on that epoxy potting solution from balancemasters that has been at dealer shows and in v-twin mag and look at its merits or not as another option on balancing out those tinglings that are shortening your riding distances, ha.

  8. 8 grayhawk May 17th, 2010 at 9:05 am

    Further; from the not so light side of the concern does anyone really want to take a perceived short cut approach to a fix if the concern is a problem.

  9. 9 Seven May 17th, 2010 at 12:05 pm

    I have a related question, Do any of those evo/shovel harmonic balancers ever work? Lots of people seem to have tried to make them but they just don’t seem popular.

  10. 10 Jim May 17th, 2010 at 6:33 pm

    Got Mine!..Love it!!…. Side car is interesting!….

  11. 11 aaron May 18th, 2010 at 1:16 am

    the TRX used a 270deg crank before the Bonneville, although Phil Irving wrote a paper in the 50’s about the concept potentially reducing vibrations in modern (for the time) parallel twins. there’s also the odd modified xs650s w/ a 277deg crank in them. It’s likely you’ll spot one of these before you see a TRX in North America, though – it wasn’t sold here as far as I know.

    Here’s a link describing the 270/277 deg crank and xs650s

    at this point, with the technology available, anything more than minimal vibration is unacceptable from a mechanical effency and longevity standpoint. Harley Davidson motorcycles shake more than others because the vibrations felt by the rider are engineered in, to make a Harley feel different than its competitors. I wouldn’t be surprised if marketing has done studies to determine the optimal frequency and amplitude of vibrations to increase sales… I’m assuming the different levels of vibration between platforms is also optimized to attract a customer that may not enjoy the vibration characteristics of the other models as much. (insert vibration joke for sportsters aka “girls harleys” here.—> did you know sportster seats are designed to be more moisture tolerant than the other models? something to do with the customer demographic and vibration… )

    No, that’s probably not true, that was my sad attempt at a joke with only seconds to think. anyways, do you really think the motor co. needs to remove the balance shaft to find a few horsepower for the rubber mount models? I’m guessing those models “feel” more powerful, more highly tuned, due to the vibration characteristics of this platform. most high horsepower bikes run counterbalancers these days… the KTM rc8r runs dual counterbalancers and is making about 150 rwhp out of a 1200cc 75deg V-twin in emissions/noise legal street trim. at least 3x what the 1200cc sportsters make, and not only does it vibrate much less, it does so while solidly mounted to the frame (unlike the current sportsters)

    oh, I should mention… as uneffecient as it is, I’ll admit that I like to hear and feel the engine in anything I operate. twins and triples, all the way!

  12. 12 J May 18th, 2010 at 1:16 pm

    Why do they shake more? Because they sense money sitting the riders’ pocket……..(!)

  13. 13 tsk tsk Jun 13th, 2010 at 12:27 pm

    Aaron, you got three things wrong A the closer to 360 deg. the better the *thermal efficiency* and the worse the vibs. (same goes for the length of the stroke longer is better BTW) the KTM quoted makes a little better then 50% more power at almost twice the rpm, and the well you were not wrong but hey fun fact Harlys only vibrate front to back, so by rubber mounting they reclaim most of what little Hp is lost by the vibs, instead of running a counterbalance shaft that losses said power.. of course *none* of that matters on the racetrack, H-D’s are just an interesting read in overall operating efficiency, they are one of the best, oddly.;-p

  14. 14 bikemike2012 Oct 13th, 2010 at 12:11 am

    There is something special about a heavily flywheeled crankshaft suspended in timkin bearings plowing massive pistons through an obscenely long strokes while somehow containing combustion through pushrod driven overhead valves that you simply cannot duplicate in any other manner. Is it sensible or efficient? Probably not… Is it the most fun you can have on two wheels? It is if you do it right. For those of you who feel the need to remove the very nature of the beast by way of suspension, counterbalancing, rubber mounting, etc. I pity you. It is you who destroyed motorcycles. Art is always in simplicity. You will simply never understand the joy of a pushrod driven twin that you personally situated in some frame configuration and rode until the wheels fell off. And until you do, there is really nothing for us to talk about. But worry not, your salvation comes in the form of battery laden electrocycles. The lack of offensive vibrations and sounds should keep you happy for years to come. Enjoy!

  15. 15 dan Mar 30th, 2011 at 4:27 pm

    I think harley outa try counter balance and rubber mounting on same engine to see how much viberation is at all speeds.It could be be a big seller,best of both worlds for some with the same sound.But you all should know they are smogging the newer harleys now,they don’t sound quite the same.calif is making them thats a shame.I think thats why harley added more c.u.i. and a 6 speed trannys in 2007 to try and make up for this.they still don’t sound the same bummer.smog on bikes is dumb and greedy,leave us bikers alone,bikes don’t pollute everything else does,

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