The only thing I'll say is I have an 11 street bob with a 96 that's got a sert pro,thunder header and a se heavy breather it made 72hp and 82 lbs.ft. Torque. I also have a 12 glide with a 103 and same setup and it made 85 hp and 99lbs. Ft torque. So they were setup the same from the same dealer. I didn't expect that much difference and the dealer is gonna retune the 96 in the spring just to see

 

A square or oversquare motor is usually a higher-revving motor, due to slower piston speeds. As the stroke increases, piston speed does as well, due to the longer distance traveled, and your red line will come down (all other things being equal). A "stroker" motor is usually "torque-ier" than a short stroke motor.

The tc88 has a 4.0 inch stroke. If you run the 4.060 "bigger bore" pistons, with a 4.0 inch stroke, you get an "all-bore "103, and if you use the 4.125 pistons, you get an "all-bore" 107. Both of which are over-square. The all bore 103 is a very different motor than the 103 motors built off the 4 3/8" stroke TC96.

The TC96 and 103 have a 4 3/8" stroke. Add the bigger bore 4.060 pistons, and get a 113, which is known to make very good power, but is still very much undersquare. To get to square, you need 4 3/8" bore, which nets you a 131. That will make big power, and I'd say, in that case, yes, square would be preferred.

Bear in mind, the mighty 120r has a 4 5/8" stroke, coupled with the 4.060 bore pistons.

Long stroke, high torque motors are naturally lower revving, which is part of their appeal in our application.

 

Right you are. Same connecting rods, same cam support plate. The running changes were applied to both. Whether or not it represents progress is another discussion.

 

I had both, the 96" (2009 streetglide) traded in for 103" (2011 streetglide),
I expected a more noticeable difference between the two, and was a little disappointed in the initial seat of the pants feel at first. But, the 103" does seem to pull just a bit harder under heavy loads, the resale value should prove to be another benefit. Overall, I've been happy with it!

 

If your gonna go big bore with your 96, go a head and take all the way to 107.


...

 

+1
No doubt, especially @ Fuel Moto's pricing.
The local dealers are nuts just to go up to the 103".

 

Are you considering a new bike just for the 103? If so, a nice 103 or better yet a 107 kit with headwork,,cans etc. Would be the way to go for a cool running powerful ride

 

Sorry for the length of this, guys -

Practically speaking, there should be no vibration difference between the 96 and the 103 since the engine components weigh the same. The 103 has the same stroke as the 96 and its slightly larger pistons are produced to weigh the same as the smaller 96 inch pistons. Theoretically, two same engines with the same stroke and the same weight pistons should have the same vibration characteristics.

There may be some driveline forces evident from the increased power but the engine vibration should be near equal. On the other hand, an H-D motor with a longer stroke IS likely to exhibit more vibration, even when properly balanced, because it creates more residual inertia with it’s larger crank/flywheel.

I hate to bore anybody with an explanation of engine balance. It can get complicated. I’ll try to do it simplistically.

The motion of a piston moving up and down in a cylinder creates a “shake” as the piston gets going in one direction and its force wants to keep it going in that direction. At the top of the stroke, the piston changes directions and heads back down the cylinder. At the bottom of the stroke, it changes direction again and heads back up the cylinder. That creates a “shake.”

Ball your fist and start punching it in and out in front of you. Your body feels the same sort of reaction to the change of motion of your fists. This is what creates vibration.

To neutralize this effect, an equal weight can be set in motion in exactly the opposite direction from that of the piston to counteract the force of the piston and equalize these forces and reduce the vibration. This is the function of crankshaft or flywheel counterweights. Extra weight is positioned on the flywheel so that when the wheel spins that weight will end up at the bottom of the upstroke of the piston and at the top of the downstroke of the piston. Hence, an equal and offsetting force to the motion of the piston is created that tends to offset the inertial forces of the piston that create vibration.

Another beautiful way of offsetting the inertial forces of a stroking piston is to have another piston of equal weight moving in an equal but exactly opposite stroke. The vibration-causing forces of each piston are cancelled out by the same but opposite forces of the other piston. This is exactly the design of the BMW “boxer” engine.

It’s sorta like getting two fat women back in a kayak once they’ve capsized (I’ve done this). If only one tries to pull themselves up into the boat, their weight or force will cause the boat to capsize again. If, however, you get both to do it in unison, they cancel the force of each other and will likely land in the boat like two flopping fish if your timing is right.

So, the flywheel counterweights work to create equal and opposite forces to cancel out one another. That’s all well and good but the problem is that the flywheel counterweight is spinning in a circle whereas the piston is rising up and down. The flywheel weight is correctly positioned when the piston is at the top of its stroke and when it’s at the bottom of its stroke. However, while the piston is in the middle part of its stroke that same flywheel weight is creating inertial force “sideways” from the motion of the piston as the weight rounds the circle while turning. This results in other inertial forces directed at angles away from the direction of travel of the piston.

Now, if you have a 90 degree twin such as a Ducati or Moto Guzzi, you cant get a little help. As that flywheel counterweight rounds up its circle away from the top or bottom of the number one piston stroke, it comes into the top or bottom of the number two piston stroke. The two pistons provide a weight-counterweight relationship in two different planes. The flywheel or crank counterweight is not left alone to spin off at 90 degrees from and create a side force that is not counteracted by another piston. Similar to the boxer twin (BMW), the 90 degree twin (Guzzi, Ducati) is inherently better designed to eliminate inertial forces and vibration.

So, the architecture of the Harley 45 degree, single pin crank motor defies total and perfect balancing since pistons and counterweights are never positioned to exactly offset each other's inertial forces. I might note, however, that H-D has constructed their "B" motor (that is used in the rigid-mount frames) employing a separate spinning balance shaft with weights designed to counteract the errant forces coming from the basic motor configuration.

Now, everything seems so simple, right ? Well, there is another force effect that comes into play : “rocking coupling.” Going back to our kayaking analogy, consider the paddle. If you take both hands and grasp them side-by-side on the paddle, alternating forces to your hands will tend to rock the paddle back and forth. This is a “rocking coupling” force.

The same holds true when attaching pistons to their crank pins. If the piston connecting rods are attached side by side to one or more than one crank pin, the same rocking coupling motion is induced as the pistons exert force on the crank pin(s).

Although the H-D 45 degree single crank pin engine design inherently has the previously-mentioned balancing problems, it does not have the rocking coupling issue that can also cause some vibration. The Harley rods are attached in a “knife-and-fork” fashion to their single crank pin so there is no rocking coupling.
The other 90 degree engines, Guzzi and BMW, have side-by-side connecting rod arrangements that do create such forces that result in some (lesser magnitude) vibration. If you look at a BMW boxer engine, you will see that one cylinder sits further forward than the other. The same is true for the Guzzi motor. Likewise, the Ducati 90 degree twin, has one cylinder offset further to one side than the other. This indicates the configuration of the relative con rods on the crank.

Can a 90 degree twin or any other engine employ a knife and fork set-up like the H-D ? Sure. In fact, the old radial airplane engines have a lot of similarities with the H-D motor. They too had a King Pin on the crank with an ingenious way of attaching the various connecting rods in a fashion that was not side-by-side. All the cylinders were attached to the crankcase in the same plane as with the H-D motor.

Why would someone use a side-by-side con rod ? This arrangement can result in a stronger rod/crank assembly that can withstand higher revs than the H-D normally ever sees. A side note is that at least one aftermarket Harley-clone engine manufacturer used to build a motor with side-by-side rods on a one-piece crank. This leads into one-piece rods and cranks versus component rods and cranks and on and on.

Anyway, I hope this simplistic digression is helpful in explaining engine balance. It may be lacking and I’m sure can withstand polishing. But, back to the basic question – I don’t think the 103 should be much more of a vibrator than the 96 considering it’s construction. I would say the same for the 106 and 107 variants. If you go to a longer stroke as in a 110, then that’s another story.

 

Hate to break the news but the MOCO quite balancing cranks years ago because engines were counter-balanced or rubber mounted. Balance factors were thrown out around 2000. the 96" only makes 2 more horse than the 88". It does make about 5 more ponds feet of torque and that is what the body feels. Vibration and power is a non issue. Just a sales pitch.

 

I think it is.....I really feel a difference. I do have a stage 1 done on my 103