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Single pin vs. Dual pin

8K views 14 replies 13 participants last post by  trjam 
#1 ·
What are the advantages/disadvantages of each?

And what is my '86 1100c ?
 
#2 ·
Although I'm not sure what your bike is, The biggest difference between single and dual is sound. Single has a more crisp, almost harley like sound. And dual sounds more "bubbley" (If you heard them side by side, you'd be able to tell them apart).

I know there's a mechanical difference, But I'm not 100% sure what it is (I've heard it many times, but I keep forgetting, I'm sure someone else will be here to fill you in on it).
 
#4 ·
A single-pin crank has a better sound, in many people's opinion. It's open to conjecture of course. My VT700 has a dual-pin crank, and I love the way it sounds, so there you go.

Anyway, a single-pin crank is arguably easier to manufacture, and has a distinct sound. A Harley has a single-pin crank. A Dual-pin crank allows the power pulses to be better balanced, since both pistons do not have to follow the same timing. This allows the spacing between the power strokes to be better distributed, and allows to better counter-weighting on the crank itself. the result is a smoother engine, and smoother power. The sound is notably different.

Also, depending on the construction of the engine, a single-pin crank allows the rear cylinder to be directly behind the front cylinder, making the engine narrower. because each cylinder has its own pin in on a dual-pin crank, the cylinders need to be offset, making the engine wider. On our overhead-cam engines, it doesn't make much different because the cam chain rides up one side of the "cylinder" and the offset internally is not visible from the outside. Inside, the cam chain is on one side in the front cylinder, and up the other side in the rear cylinder. So, the cylinders are offset but you can't see it that way from the outside. Pretty spiffy!

Hope this helps!

--Justin
 
#7 ·
the 1st v twins made by indian or hd were single pins. different than a single pin shadow though. shadow single pin v twins have connecting rods that BOLT to the one piece crank,just like a modern car engine. indian and hd connecting rods are a complete circle on the big end.

the crankpin is pushed through them,and then bolted to the flywheel halves. after that the flywheel is trued and torqued. not a whole lot of people still around that are really good at this.

depending on which year hd or indian you are working on,the flywheel/crankshaft assembly could be as many as 5 seperate pieces not including the connecting rods.

also,as mentioned,twin pins are smoother running and typically make more power that their single pin counterparts. i have owned both styles (in many different brands and sizes) and it is kind of a personal preference thing.
 
#9 ·
gyjoe said:
If an engine with a dual-pin crank is better balanced and smoother than one with a single-pin crank, does it follow that the dual-pin engine will last any longer?
generally...yes

The internals will take less of a beating since the forces are more evenly distributed during the assembly's rotation.
 
#12 ·
When I bought my 97 Spirit, I opted for more HP and smoothness over the ACE single pin, which had more torque. The ACE was de-tuned a little bit to prevent it from shaking itself to pieces.
My Spirit revs to the moon. Fifth gear is almost unnecessary. You can't kill it. But the exhaust (even with Samsons installed) sounds like a Chinese garden tractor (if there is such a thing).
A matter of personal preference. I can see why people prefer single pin, that's what Harleys sound like.
Whatever you ride, Ride Safe and watch for the idiots.
 
#14 ·
mike1 said:
But the exhaust (even with Samsons installed) sounds like a Chinese garden tractor (if there is such a thing).
A matter of personal preference. I can see why people prefer single pin, that's what Harleys sound like.
The single crank pins do sound so much better to me. The Chinese garden tractor is a new to me (and accurate) description of the dual crankpin sound. I've also heard the dual crankpin sound referred to as:

A 600 pound lawn mower
An old motorboat
An elephant farting under water

(the last two were by Cycle World describing a VTX 1800 dual crankpin with aftermarket pipes. See December 2004 issue page 45.)

In spite of the sound, I do like the smoothness of the dual crankpin setup.

Like tubes_rock, I did love the sound of my dual crankpin VT700. For some reason, maybe the pipe lengths, it did make a lot better sound than my 1100.
 
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