Ok so i sold my 2012 SG and bought a 2012 Fat boy.
Both bikes are stock. And I weigh 225 Lbs.
The difference i am noticing is when casual crusing like around town when I upshift with the Fat Boy if i don't take the rpm's up to at least 2900 rpm before upshifting when I get to the next gear my rpm's are at or below 2200 rpm's.
This seems to give me some slight lugging as I accelerate until i get up to 2300 or higher rpm's.
If I take the rpm's up to 3000 or higher rpm's before an upshift then when I am in the next higher gear my rpm's are 2300 or above and I don't seem to get the lugging as I accelerate. But for casual cruising going to 3000 rpm and above seems like it would be a bit excessive.
With my Street Glide I noticed I could upshift at 2700 to 2800 rpm's and when I got into the next higher gear I didn't notice any lugging at 2100 to 2200 rpm's.
So what i am saying is my bike seems to lug slightly at 2200 rpm when going up through the gears causally .
If I am riding on a level road and riding at a constant speed, I can ride at 2200 rpm with little to no lugging as long as i don't try to accelerate.
I would think that my 103 FB would have as much low end torque as my 2012 103 SG, but it seems it doesn't.
Is this normal for a stock 2012 FB? Am i just feeling the difference between the solid mount engine vs the rubber mount engine?
And do you other stock 103 fat boy owners notice this same thing?

 

I don't know about the gear ratios, I suppose one could find out, but I would guess with a bit of confidence that the cams are different with the SG coming on earlier to accomodate the heavier bike. Also, the pulley ratios probably different as well.

 

compare both bike's gearing, motor sprocket, clutch, tranny sprocket, rear wheel pulley and individual trans gears and I'd guess you'll probably find some differences

 

If people just use it the Harley website is a wealth of information.

http://www.harley-davidson.com/en_US...are-bikes.html

 

Thanks for the link. I can see the ratios are a bit different, but I would also like to know if other 103 softail owners have noticed this same type of performance from their softails as I have?

 

Interesting. I had a 2010 FatBoy with a stock 96" engine. It was my first street bike. I would often find myself on level ground at low RPM and if I rolled the throttle on slowly, I could do so from about 1500 in the lower three gears. The bike would accelerate like a rocket from 50 mph in 6th gear. Now I realize that below 2000 was too low an RPM to utilize. However, the scoot would pull with no complaint whatsoever. In fact, I found that the "B" engine did not seem to like to rev higher as freely as the "A" engined 103 in my '13 Road Glide. I COULD rev it, but it would sort of tell me "do we really need to do this"?

While cruising around on the FatBoy, I was almost never doing so at 2900 RPM...more like 2100.

 

Also, it's more than "rubber mount vs. solid mount." The counterbalancer in the B engine makes it seem and respond quite a bit different. Then there is a different exhaust system, much larger mufflers on the SG, etc.

As a matter of fact, I always surmised that the heavy flywheel effect of the counter balanced B engine made the low speed chugging more feasible.

 

When my softail was stock it was a real lazy dog performance wise, once I built the engine out it became a beast. But my dyna would spank it on the street, if I could only learn to ride them at the same time to be sure.
I think its the rubber mounted vs counter balanced. Every softail I've ridden seemed soft compared to a rubber mount engine.

 

OK I wonder if maybe my speedo or tach is off.
Can anybody tell me if 2500 rpm in 3rd gear at 40 mph sounds right on a 103 FatBoy?
Or if 2500 rpm in 4th gear at 50 mph sound correct?
This is what I am seeing and the bike likes to cruise in that 2500 to 2600 rpm range.

 

I've looked at my tach at those speeds every time I ride, but I'll be damned if I can remember off hand. I think I'm running right at 2900/3000 rpm at 40 mph in 3rd.