I have a '07 Fatboy. I have about 32k miles. I have V&H Short shots with V&H Fuel Pak (Set properly) and a HD high flow air cleaner. I also (now) run AmsOil engine and Redline Tranny and Primary oils. Other than that I have no other mods mechanically. My problem is the bike with run great from 1-5 gears. Once I get to 6th regardless of speed I have strong vibration and the engine lugs down. I used to get about 48 MPG when the bike was new, now I get about 37 on the highway. I changed fluid type from standard HD to Synthetics thinking that may help to no avail. Any suggestions? Has anyone had or heard of this or a similar problem?

 

Can't see it being the trans. 6th gear puts a ***** of a load on the engine. This will show up as a lack of power from the engine itself. Could be injectors, leaky valve or lot's of things. I'd be looking at the engines output first.
Ron

 

What speed do you run in 6th gear?

 

My 2007 is in the shop for the 6th gear bearing going bad. I did not have any vibration, but did have noise everyone I used the clutch while cruising. Might be related