I see that this is an old thread but my one year old Heritage Softail has the same issue. The throttle is very notchy and stiff feeling. Low speed riding under 45 mph is very annoying. I like to ride back roads at low speeds and it drives me crazy trying to maintain a steady speed. It's like: on, off, on, off, for the whole ride. My car is drive by wire and it's smooth as silk. If there is a aftermarket kit out there I would pay any price for a fix. If there is a better spot on this site for this question please redirect me. thanks

 

see post #12...worked for me.

 

I have a 2012 SG and my throttle is sticky only if I ride it to work and it's sitting out in the sun until I get off work. Then it's sticky but loosen once riding. I have rubber grips so I'm thinking it's the grips swelling while in the sun.

 

my 2011 ultra did same thing. I am on my 3rd set of grips. I used screaming eagle this time amd also replaced the throttle motor. Has lasted quite a while now

 

The twist grip sensor can indeed get notchy. There are plenty of other causes for for binding twist grip action, all covered above. My 08 Road King with 93,000 miles now has the notchy twist grip sensor, verified by rotating the sensor without the handgrip installed, then with the sensor removed from the bike. Still notchy. So far the only thing that has improved things is Dupont Dry Lubricant dispensed from an aerosol can, a short squirt into both ends. On mine, there is room enough for the straw to be inserted beside the handle grip heater wire in the center of the inner end to get the lube in there. I fully anticipate this will be a temporary fix and the only long term fix will be sensor replacement. Hopefully that would be good for another 11 years and 93,000 miles. If you have a machine still under warranty, let the dealer work it out. The techs should know about positioning induced problems and make adjustments. If the problem remains, I would have the shop owner or manager take the machine around the block and decide if this were his machine, would he put up with it? This malfunction doesn't put you dead on the side of the road, but becomes increasingly irritating and unacceptable as the miles pile up.

If anything has jammed the twist grip inboard, that could have moved the switch box just enough to cause new binding. If there have been no accidents, warranty should take care of it. (Show me the new machine on the sales floor with the notchy throttle action).