Why do Sportys vibrate?
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Road Master
Joined: Dec 2014
Posts: 994
Likes: 43
From: Essex, England
Why do Sportys vibrate?
Talking to a guy whilst getting fuel the other day and he told me he took an Iron for a test ride a few years back, but decided he couldn't live with the vibration and asked me if I knew why did they vibrate as much? The dealer (rightly?) said its just part of what makes a Harley a Harley.
I said I didn't think mine is that bad to be honest and said my SV650 used to give me numb fingers and I dont get anything like that from the Harley. He said he has had a SV and a couple of other big twins (Honda, Aprilia) but kept saying he didn't understand why the Harley had such shaking vibration?
He wasn't knocking them, he was just curious as to why they dont have any crank counter balancing or suchlike, or is the shake designed/left in, as the dealer said, as being part of a Harley's character?
I've been thinking about it ever since. Do 45 degree twins just produce that effect? Could it be balanced/smoothed out if Harley wanted to? Are the bigger engines the same?
I said I didn't think mine is that bad to be honest and said my SV650 used to give me numb fingers and I dont get anything like that from the Harley. He said he has had a SV and a couple of other big twins (Honda, Aprilia) but kept saying he didn't understand why the Harley had such shaking vibration?
He wasn't knocking them, he was just curious as to why they dont have any crank counter balancing or suchlike, or is the shake designed/left in, as the dealer said, as being part of a Harley's character?
I've been thinking about it ever since. Do 45 degree twins just produce that effect? Could it be balanced/smoothed out if Harley wanted to? Are the bigger engines the same?
Road Captain
Joined: Mar 2009
Posts: 570
Likes: 2
my 2007 softail has the tc96b engine...almost no vibration...hd incorporated a counter balancer for the crankshaft...this leads me to believe that the crankshaft rotation and the vtwin firing sequence causes the vibration...please don't take this for granted as i'm no expert...
anyways hd could eliminate most of the vibration, they did it in the tc96b engine
see this animation...
http://s370.photobucket.com/user/ken...ngine.gif.html
anyways hd could eliminate most of the vibration, they did it in the tc96b engine
see this animation...
http://s370.photobucket.com/user/ken...ngine.gif.html
Seasoned HDF Member
Joined: Aug 2011
Posts: 5,289
Likes: 3,436
From: Idaho Panhandle
I keeps my girlfriend smiling. When she enjoys the ride, I enjoy the ride later.
She also enjoys the pipes, which has nothing to do with this thread, but I've had way too much coffee this morning.
She also enjoys the pipes, which has nothing to do with this thread, but I've had way too much coffee this morning.
Cruiser
Joined: Sep 2012
Posts: 176
Likes: 12
From: in a house
Watch this animation and see if it doesn't become crystal clear (push the button in the corner to see the internals):
http://www.animatedpiston.com/Evo.htm
There is a lot of mass rotating around connected to a single crankpin. It's like having all of your laundry on one side of the tub and expecting the washer to not dance across the floor on the spin cycle.
To compound that problem the narrow V angle means the firing order is something like BAM..BAM............BAM..BAM............ where-as a wider angle would be like: BAM....BAM....BAM....BAM....
It IS a Harley trait, a by-product of their design.
http://www.animatedpiston.com/Evo.htm
There is a lot of mass rotating around connected to a single crankpin. It's like having all of your laundry on one side of the tub and expecting the washer to not dance across the floor on the spin cycle.
To compound that problem the narrow V angle means the firing order is something like BAM..BAM............BAM..BAM............ where-as a wider angle would be like: BAM....BAM....BAM....BAM....
It IS a Harley trait, a by-product of their design.
Last edited by NooneOfConsequence; Oct 12, 2015 at 11:46 AM.
Seasoned HDF Member
Joined: Jul 2011
Posts: 27,097
Likes: 4,676
From: Frozelandia, Minnysota
Both pistons fire on the same rotation, then both exhaust, repeat. Couple that with the single crank, and it has close to the pounding out of balance feel a basic single cylinder motor has. Personally, I wouldn't mind a counter balancer in all Harley motors, be nice to tell if that's a cop car or a semi in the rear view... 
Cruiser
Joined: Jun 2015
Posts: 196
Likes: 11
From: San Diego
"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."
Or what I like to say.... "Potato-potato-potato"
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."
Or what I like to say.... "Potato-potato-potato"
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Seasoned HDF Member
Joined: Sep 2007
Posts: 9,741
Likes: 1,599
From: Danbury CT
You do know that all softails are counter balanced and solid mounts and don't vibrate and all touring, dynas and sportsters are not balanced and have rubber mounts.
And the rubber mount design smooths out on acceleration.
And the rubber mount design smooths out on acceleration.
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Banned
Joined: Sep 2013
Posts: 1,127
Likes: 226
From: middle Tennessee
My 2014 Super low 883 hardly vibrates at all. The mirrors are clear up to 80. When I got it new it vibrated between 50 and 55 enough to blur the mirrors. As I put the miles on it it started to smooth out some. I put some vibranators in the bars and now I hardly notice any vibrations. Its a joy to ride.