Q & A: What gives a Harley-Davidson motorcycle its distinctive sound?

How Stuff Works ^

[yankeedame]

What gives a Harley-Davidson motorcycle its distinctive sound?

There is no denying that a Harley-Davidson motorcycle has a unique sound, especially if the mufflers have been removed! Even with the mufflers on, however, it sounds different from other motorcycles. The reason for the sound has to do with the way the engine is designed. If you have read the HowStuffWorks article How Car Engines Work, then you know how a basic four-stroke gasoline engine operates. A piston goes through the intake, compression, combustion and exhaust strokes every two revolutions of the crankshaft. When your lawn mower is idling, you can hear the pop-pop-pop-pop sound of the individual strokes. What you are actually hearing is the sound of the compressed gases in the cylinder escaping when the exhaust valve opens. Each pop is the sound of the exhaust valve opening one time, and it happens on every second revolution of the crankshaft.

In a two-cylinder, horizontally opposed engine, the pistons are timed so that one fires on one revolution of the crankshaft and the other fires on the next revolution -- so one of the two pistons fires on every revolution of the crankshaft. This seems logical and gives the engine a balanced feeling. To create this type of engine, the crankshaft has two separate pins for the connecting rods from the pistons. The pins are 180 degrees apart from one another.

A Harley engine has two pistons. The difference in the Harley engine is that the crankshaft has only one pin, and both pistons connect to it. This design, combined with the V arrangement of the cylinders, means that the pistons cannot fire at even intervals. Instead of one piston firing every 360 degrees, a Harley engine goes like this:

A piston fires.
The next piston fires at 315 degrees.
There is a 405-degree gap.
A piston fires.
The next piston fires at 315 degrees.
There is a 405-degree gap.
And the cycle continues.

At idle, you can hear the pop-pop sound followed by a pause. So its sound is pop-pop...pop-pop...pop-pop. That is the unique sound you hear!

[MarkL]

Thanks!

Mark

[Melas]

My Harley has more in common with your bike in that regard than with the biker who you met. My bike is virtually maintaince free and computerized. I don't carry any tools, and certainly no spare parts.

My speedo gets information from a sensor, not a gear. I don't have a kick start with magneto, but a batery, an electric starter and a modern charging system. I don't have points but a digital ignition with multiple timing curves. The bike is timed by rotating the modular ignition itself. As a matter of fact, like most modern

[JoeSixPack1]

I just put two new tires, 3 sets of brake pads, new handlebar starter/kill switch, new starter clutch & re-rewired the rear signals. (+oils,seals,gaskets,etc.)

Now my ride is 10 years old and nearing 90K. Stuff wears out.

I'm in the midst of a 'now and then' starter problem. But I think I got it. :-)

But , today and today only, the cash price of my bike, if I was selling, would be less than after I'm back in the saddle. It also is referred to as "That chrome SOB piece of AAARRGGHHHH!!!! :-)

AAAARGGGGGGGGGGGHHHHHHHHHHHHhhhhhhhhhhhh ANd I got dirt in hair!!!!!!!!!

[Betis70]

re-bookmark.

It's all about the single pin v-twin, right?

[LizardQueen]

I've got an older Suzuki GS500 parallel twin that sounds like a lawn tractor :lol:.

And DH's Honda (919, fuel injected 4) sounds either like a sewing machine (at low revs) or a bee (at high ones).

LQ

[BraveMan]

Yamaha FJR1300. A nice bike by any measure . . .

I like Jap Tech as well; always have. I've owned a few myself; a '75 Kawasaki H2, a 78 Kawasaki Z1-R, an 81 Honda CB750F, . . .

My riding style has changed as the years have rolled by; luxury, comfort and style are more important to me now than acceleration, cornering prowess and bleeding-edge tech. Twenty years ago the opposite was true. Twenty years from now, who knows? I doubt I'll enjoy the Leviathan I'm currently riding as much twenty years from now as I do at this moment. Then again, I never thought I'd hang on to the FXRS for twenty+ years either.

I am mindful of the fact if it weren't for the competition from the Japanese onslaught my FLH wouldn't be near the quality piece it is today. All that being said, I have no intention of unrolling the tool pouch on the new bike; I don't want to get any fingerprints on the shiny tools inside . . . ;o)

[martin_fierro]

I got just the thing for ya:

[HairOfTheDog]

There is no denying that a Harley-Davidson motorcycle has a unique sound, especially if the mufflers have been removed! Even with the mufflers on, however, it sounds different from other motorcycles.

Ah yes, the subtle difference between "obnoxious" and "even more obnoxious".

< /unpopular opinion >

[JoeSixPack1]

From the 101 reasons to own a Harley:

#81. So you can have nice, wide, soft seat to fit your old, wide, soft butt.
#82. When people ask "Isn't there a waiting list?", you can tell them "Yeah, I waited 33 years and 9 Jap bikes"

I never touched a thing on my current bike for the first 6 years I had it. If it weren't for scheduled maintenece (oil, filters, brake pads, etc.) I would have been hardpressed to say what would make it stop running! :-)

[JoeSixPack1]

It's my starter relay behind the headlight.
I'm headed to the local chrome toy store to pick up a relay and a failsafe plunger/push-in starter cap. (It bypasses all the electronics and engages the starter manually).

You can use your ether to keep your hair in place (or your brain out of place)! :-)

[blackie]

I had a '91 Sportster and rode it until 2000 when I sold it to a Deputy Sheriff buddy of mine. It was an easy ride around town ride as it's pretty low to the ground, I have a 28.5 inch inseam and could flat foot both feet at rest.

I thought I was all through riding ~ two weeks after I sold it, I got the bug again and ordered a '01 SV650. I love it!

That new 1600 Vulcan Nomad, for $17K+ is a good buy if that's your kinda ride.

[uglybiker]

Gee whiz, blackie. You just might have to check out these nifty little 650's. ;-)

[blackie]

I have checked them out, my Triumph dealer buddy just took that brand on and has 8 of the beauties right now.

Their suspension is first class, the engine is very similar to the SV650, it is only down a couple of horse power to the SV650. It's fit and finish is excellent!

[Cogadh na Sith]

I just gave it the 600mi break-in oil change, final drive fluid change, throttle body sync'ing and the once over.

I like it.

[SFC Chromey]

These are awesome, don't forget that Storz Performance has flat track kits for the Sportsters too! They are just the cosmetic stuff, but as with any H-D engine parts are ALWAYS available.

http://www.storzperf.com/xr1200.html

(Still haven't learned how to post pictures!)

[MarkL]

I've seen that bike, but for me, it's just not right. One of the things that I love on the XR-750 is the port arrangement. The intake ports are on the rear of the heads, the exhaust ports on the front. This allows you to have a pair of staggered carbs with big K&N filters on the right side, and the exhaust pipes on the left side of the bike. I know, it probably sounds silly, but hey, that's what turns me on!

Mark

[SFC Chromey]

Yup, like a true flat-tracker. You have your steel shoe?

[spunkets]

" So its sound is pop-pop...pop-pop...pop-pop."

Potato, potato, potato... unless it sounds like a duc.

[BraveMan]

I've occasionaly stalled the Bagger trying to pull away immediately after starting it. Whenever I do that, the ECU goes into "dumbass mode" & cranks the idle up to 2000 rpm for the next two minutes, until its happy with my ability to not stall it anymore.

I hate that . . .

[biblewonk]

I just saw Harley oilfilters at walmart. They were almost 10 bucks when all the rest were about 6 bucks.