I have an 05 883 Sporty. It absolutely loves to cruise around 65 mph. Now here in California 65 mph is a good way to become a new hood ornament. I can comfortably get up to 70 mph with little "buzzing" but after 85 mph its just uncomfortable.
SO that being said, I believe that Sportys were made to cruise around town, take on some twisties, and just cruise down some back roads. They can surely keep up on the highways with no trouble, BUT unless youre a woman, you wont appreciate the vibrations once it gets up to about 80mph!

 

Change the front pulley to 32T on a 883 and you are at the same gearing as the 1200...it's stout enough to pull it. http://sportsterstuff.webs.com/apps/documents/

 

I really like this bit of information. Would be incredibly useful with a 1250 conversion.

 

Add more teeth to your trans pulley or subtract teeth from your rear tire sprocket. Change to much and you will have to get a different size belt. Worth the trouble if you are always at freeway speeds.

 

My cousin and I were doing between 80 and 90 back from vegas last night talk about screaming! Still had enough power to speed up though. Best of all I managed 52mpg!!! I was probably riding less than 15 feet from his suburban though.

 

Can't speak for the 883 but on my 1200 if I shift into 5th before 60mph the bike is miserable.

 

Yeah I shift into 5th at 65-70mph usually. After already being in 5th anything less than 60 requires down shifting. I have a 45 minute drive to my second job and I'm doing 80mph 95% of the time. Quickly speeding up to 90-95 to pass the dumb asses that slow down to 65 next to cars but then speed up to 80-85 once it's clear instead of getting out of the fast/passing lane.

 

I thought my 883 was screaming at 70 until I learned to stay out of 5th until I hit about 65.. then it sounds "normal" at 70-80 in 5th.

 

I cruise my iron at 80 all day ... No issues at all even at 100 mph I feel like the only thing is lack of aerodynamics lol bike ride smooth and zero issues how big are you Nd how much you weigh ? Im only 5'9 155 so that might make a difference

 

I was on the highway here in PA yesterday and the winds were howling here. It was uncomfortable as the winds was really shaking my bike, but other than that is was ok at highway speed.