16 Heritage with 8kmi, stock 103HO motor. I purchased this four thousand miles ago with stock air cleaner, stock head pipes, and slip ons. It accelerated great up to 80mph but then flattened out, took a bit to get to 90, and forever to get above that. I changed the exhaust to Bassani true dual head pipes, 36” fishtails, PM air cleaner, and complete tune via FP3. It actually got a little bit worse on top end but gets to 80 faster now. It will also burn through 4gal of fuel at 80mph in 118 miles! No way this is correct?

Does anyone else have this issue?

 

Harley’s aren’t known for their speed.
My 09 Heritage might make 100mph with no head wind.

As as for the 29mpg at 80mph; that’s about what I get.

 

Makes no sense, my 11 Road Glide with a 103 gets much better mpg and will run 120+.

 

Doesn't sound right to me. My 2017 Fat Boy can be doing 90 in 4th in a hurry. Not sure what to tell you though.

 

After looking back at a previous post I see that the 29mph I got was riding in a strong head wind.
Both my Son and I have 96ci Heritages and we both got the same mpg last year where-as on a trip where we mostly were cruising around 80 mph- we both got between 32-35.

 

Yeah, 30ish mpg is fairly normal at that speed. 70 or less you should be in the 40 mpg. As to the speed, I'd say something isn't quite right. My 07 with a 96ci will go straight to 120mph. The rate of acceleration drops a little after 100, but it's still good. I don't make riding that fast a habit though..

 

While Harley's aren't barn burners.... that sounds a little sluggish, especially on top end...

MPG will be dependent on soo many factors.... I have a 103 bagger (STAGE I, EFI), 95 Heritage (STAGE III, EFI), and '01 88 (STAGE I, carb).... around my house is freeway with 70mph limit and 75-80mph traffic flow. There are also hills. If I ride the freeways to get around I get 36, 35, & 38..... The higher the freeway speeds, throw in a little headwind, and I'm in the low 30's on all three...

All three will get high 30's /low 40's for mileage, if I ride the tw- lane back roads with a 55mph limit..

My Heritage will get to 90 easily, and will hit 100mph...

If your top speed is the only thing affected, all else being in good shape with a good tune, that suggests an air/fuel restriction issue ... If the MPGs are suspect as well as top speed, then that suggests an air restriction issue...

Since your bike is pretty new, with low miles, it's hard to suggest a dirty/clogged air filter..... but.... have you checked the air filter recently? If you have a bike that kicks a lot of oil mist out through the crank case breathers, it could be your air filter has absorbed enough oil to restrict it's capacity at high load, high RPM running... Worth a look...

Good luck with the fix....

 

I'll burn about 4 gallons every 130 miles at 80 mph. Dropping the speed down to a tad below 70 mph will up the mpg to 36-38 and down to 60 mph or so will bump up to 40 mpg.

But the speed you're experiencing is not right. I have a Performance Plus Stage I with fishtails (Sampson) and accelerate briskly up to 90 mph, then it starts falling off a bit. Fastest I've gone is 105, but it had more.

Mine's a 2012, 103.

We see what you're experiencing quite frequently. Here's a LINK with the things to look at to track down what's going on.

Usually it is one or more of the following:

Filter Element
Gummed up throttle body
Tune
Plug wires
Reversion in the exhaust
Too much heat

Sometimes we see engines that have had heat damage (it can happen in less than 10K miles of the factory "they all are like that" set up) that get real doggy. Leakdown test is the way to find out.

Here's an article LINK on how to get the most out of your bike, regardless of what mods have been done.

 

my '15 slim would hit the century mark easy...I wouldn't do it often or go over that much since the front starts feeling light. might not hurt to run some Lucas or sea foam through the tank to clean the injectors.

 

My wife had a 2013 Heritage with the 103, and when I first rode it, I noticed compared with my 2011 96 it was a dog, my factory 96 would run rings around her 103 and her uncles 2011 Ultra 103 was had way more power than either of our bikes, so I did some research and at the time there were four different 103 engines, the engines used in the touring bikes had more power.