Topic: SOHC'S ARE SMOOTH, BUT WHY DO THE HARLEYS SHAKE SO MUCH?

[jcarthel]

SOHC's are smooth both at idle and at high rpms?  Why is it this way?  What was done by Honda to make them so smooth?  I am also wondering why do all the Harleys I see shake so much at idle?  Do the Harleys shake and vibrate at higher rpms too?  Why do the Harleys shake so bad at idle?  Are their motors very unbalanced? 

Justin

[nobody]

Correct me if I'm wrong but the Honda 4s are smooth because they fire opposite of each other while the Harley Vs are designed with a slightly "off timing" crank that makes them fire at odd intervals. Where a Honda will go "bang bang bang bang" a Harley will go "bang bang pause bang bang pause".

Or something like that, I saw some show where they explained why Harleys have such a distinctive sound.

[noahspop]

i ride my aunt's nightster and it feels like it's gonna jump out from underneath me. don't get me wrong it is nice,  but its not a honda.
i'm always given her #$%* about her harley, and vice versa, but hey we all ride and that's what really matters.

[Don R]

They auctually patented (or copywrited) the sound. The rods both connect to the same journal on the crank. That kept them from firing directly opposite in the order so yes they go, bang bang pause, bang bang pause. Thats why other v twins don't do that or sound that way.

[kos]

NO...they did not get the patent on the firing order and the sound.  HD is a very small factory compared to Honda LTD of Japan.  HD makes, at best 310,000 m'c/s a year Honda makes 1.2 million.


Give me a break, hd's are junk.

KOS"

[bucky katt]

at or near 5500 rpm's a harley motor is done.

[mystic_1]

Based on the junkmail catalogs I get from them, it seems like Harley Davidson is mostly a clothing manufacturer these days

My brother's Road King looks like the engine wants to go walkabout from the frame at idle.

There's no technical advantage to the common-crankpin design aside from space savings, i believe they still build them this way out of tradition more than anything else.  Their newer engines (vrod etc) move away from this design, but they've made such a fuss about "a harley engine is build a particular way" that when they try to introduce newer designs a lot of people say "that's not a real harley".  It's an interesting hole they've dug themselves into, in that regard.

mystic_1

[faux fiddy]

Harley 45 degree Ducati and most Asian stuff is 90.

The bang bang pause bang bang and two compression strokes 45 apart make for torque and also make it very suitable for dirt track as the back wheel breaks free easier.

[smokeygold]

Hate to disagree with some here...however, they are not junk and they do control a very large share of the market. In fact, the folks at Harley are marketing experts. I own both brands so I do know what I speak of. They are engineered for the market they are going after.
They command large dollars and in most cases sell out every year (very few left over). Thre are far more Metric leftovers every year.

[crazypj]

Harley was going for 500,000 units but cut production and started closing factory at least a year before recession.
 There were a lot left over and dealers were discounting them.
They realised they cant compete with Honda so are going back to being a marketing company.
 You can only sell so much relying on 'history' and misplaced patriotism (If you want an all American motorcycle buy a Victory or Goldwing)

 Take a look at Dinamoto site
 http://www.dinamoto.it/DINAMOTO/on-line%20papers/twin%20motors/twin.html
scroll down to the animations. Harley has been removed but it was similar to single cylinder.

PJ

[GammaFlat]

Those animations are awesome.  A picture.... er.. um.. video says a thousand words. 

[KB02]

You can only sell so much relying on 'history' and misplaced patriotism (If you want an all American motorcycle buy a Victory or Goldwing)

While I agree with the sentiment (completely agree), Honda has stopped making the Goldwing in the US. They converted the plant over to cars I heard.

And a Harley engine will smooth out at speed, but that's if you can keep from getting shook off while at idle and lower speed enough to get up TO speed. 

I shouldn't complain too loud as I DID like the Buell line of bikes. Shakey as hell at idle, but MAN those things could carve. I like my Ducati, though. 

[Raul CB750K1]

I don't think that the vibration comes from the firing interval, but instead, from the engine configuration.

My sanglas 400CC has a huge cilinder, 83.5mm diameter, and a massive flywheel. Have you ever heard "it idles so slow you can count the explosions"? Well, I have managed to do that thanks to the big flywheel. 400 rpm ar attainable, it means 200 explosions per minute, or 3.something explosions per second. You can really distinguish them, but the idle must be raised a little if you want smooth transition from idle to slow speed.


Long story short, while the bike rests in the centerstand and you rev the engine, the bike moves!!!! The inertia involved in the big piston going up and down create such a vibration that can make the bike slide while on the pavement.

On the contrary, multi-cylinder bikes have smaller parts to achieve the same displacement, and therefore, the inertias are smaller. There are many V-twin's out there, just get any Yamaha or Honda catalog, and many of them have the same, if not bigger, displacement than Harleys v-twins, but japanese engines have delicacies such as contra-rotating weights to cancel the inertia effect.

[MJL]

At one time Honda (Or some other import company) built a 180* firing v-twin cruiser. It was a smooth motor and had more power. However, people complained that it did not sound like a Harley.  So as any good company does, they built what the customer wanted and changed to a single pin crank.

How about a parallel twin? I've heard stories of xs650's dancing on the centerstand at idle.

[Hush]

4 smaller pistons on a balanced crank are always going to be smoother than 2 pistons firing in different directions.
I kinda like Harleys in a straight line but as soon as I get to a corner I want my Honda back.

[754]

Kos, why not tell us how much of the heavyweight (over 1000cc) market share Honda has, it is far less than HD..

 In fact it has only been in the last 10 years that the Big (Japan) Four combined heavyweight sales, have finally exceeded HD production.

 The main reason HD builds their core product is demand.. if the demand stops, they might  change what they build..

 Times sre getting tough for them right now, but that probably means every bike manufacterer, is experiencing lower sales. Hd has survived over 100 years, what is happening now, is not the worst they have seen..

[Jerry Rxman Griffin aka MuthaF'er]

My Harley is not junk. It is a better bike than my 750F AND unlike the 750, it does NOT leak oil. Of course my 750 is 34 year old technology and I have beat the #$%* out of it. I don't take it easy on the Harley either though. Plus the Harley has more miles and has NEVER had the first problem.

Harley worked with Porsche to help smooth out some of their engines with a counter-balancer (plus build the V Rod engine). Mine is that 88B engine. Still has the Harley sound. It may not be as smooth as a Honda but it doesn't bounce around in the frame like the previous models had. Very tolerable. That bounce and the sound would be considered a Harley trademark.

[72 yellow]

At one time Honda (Or some other import company) built a 180* firing v-twin cruiser. It was a smooth motor and had more power. However, people complained that it did not sound like a Harley.  So as any good company does, they built what the customer wanted and changed to a single pin crank.

How about a parallel twin? I've heard stories of xs650's dancing on the centerstand at idle.

You should see the front end shake on my 71 BSA Lightning at idle.

[MJL]

They realised they cant compete with Honda so are going back to being a marketing company.

I've been saying for awhile that Harley doesn't sell bikes, they sell an image.

My local HD dealer has more floorspace devoted to clothing that to bikes.

[Hush]

My sister-inlaw waited for 6 months for her new Harley to replace the old model, she rode it home 6 miles and it spewed oil like a baby on steroids.
To Harley's credit they came and picked the bike up and replaced it with another complete bike, sad part is 10 miles later some tintop changed lanes in front of her and took the whole bike out.
I guess if you really want a Harley then that's what you should buy, I'm not that keen on the new big Kawasaki Vulcan cruisers or the rediculous Victory "scooter" either.

[754]

Japanese bike owners used to  slam the way HD was built..

 At first the Japanese resisted building cruisers, then they finally did..
 No matter what they would try , it would surely be better.....would it not?

 Hydraulic valve adjustments, overhead cams, newer, smarter designs.. superior engineering...

 So they started building cruisers, they tried this and that, surely the Big Four would show their superiority...

 So we wait, and wait for that to happen... Did any of them make a big dent?.. not that I can see..

 Kudos to the Fury though, first bike out of Japan that looks like a real chopper frame, you could actually stick just about any motor in it, and it would look great.. too bad it did not come out 10 years earlier..


 I love my SOHC 750s, but am not interested in any of the newer Japanese stuff.. The new honda 1100 twin shock?.. I would take a 1200 Sportster over it, any day..

[Deltarider]

I've heard stories of xs650's dancing on the centerstand at idle.

They sure do. No balancing in there.

[paulages]

At one time Honda (Or some other import company) built a 180* firing v-twin cruiser. It was a smooth motor and had more power. However, people complained that it did not sound like a Harley.  So as any good company does, they built what the customer wanted and changed to a single pin crank.

How about a parallel twin? I've heard stories of xs650's dancing on the centerstand at idle.

You should see the front end shake on my 71 BSA Lightning at idle.

yeah, that always cracks people up, huh? the front wheel actually rolls fore and aft a good couple inches at idle. do you have "reverse" too? ...on smooth concrete (like my shop floor) mine will scoot backwards if i rev it while on the center stand. also good for laughs.

in regards to the original question: generally speaking, the fours are inherently balanced in that every reciprocating part has another piston doing the exact opposite thing. similar to the boxer design (BMW for example) in a way, but that is of course a twin and the pistons are literally opposite each other on the crank, balancing each others forces out more or less. balancing a crank is all about figuring out which forces you want to reduce, as there are multiple forces happening at once. with most twins, you smooth out one and another gets worse. there have been many schemes through the years to get over this, but in the end a twin is almost always going to have the vibes.

[ofreen]

There's no technical advantage to the common-crankpin design aside from space savings, i believe they still build them this way out of tradition more than anything else.  
 

One advantage is that there is no rocking couple vibration with the Harley (AKA knife and fork) set-up such as there is with the BMW, or other twins with offset crankpins.

in regards to the original question: generally speaking, the fours are inherently balanced in that every reciprocating part has another piston doing the exact opposite thing.

Inline 4 cylinder engines have perfect primary balance, but have a considerable secondary imbalance.  This second order vibration is at twice crank speed and accounts for the buzziness that inline fours have.  A lot of people find this higher frequency vibration more objectionable than lower frequency vibes from a twin such as the BMW (or a Harley.)  Of course, many designs, both 2 and 4 cylinder, now make use of one or more counterbalance shafts to reduce vibration.

Any v-twin with cylinder angle of less than 90 degrees is going to have a primary imbalance.  The Harley at 45 degrees is gonna shake.  The newer counterbalanced engines smooth out once underway, but resemble a paint shaker at idle.

[Inigo Montoya]

I cant say I care about HD that much. Not so much the bike, though vibration and the weight keep me away. The biggest issue I have is the image thing. I do not care about the image but once you buy HD, you will be subjected to it anyways. First you got people doing the "it isnt a bike unless it is a harley" and once you get there, the same people then go further and give you crap if you get a sportster unless it is a 1200. Sorry but I just do not care about a 600+ pound bike that has less performance stock, than a 600 rocket and image should not control what a person rides.
I will not say they are junk, they once were but not so anymore but I just do not see them worth the cost in any way.