What would cause the throttle to stick at the hand grip

Check throttle and idle cables are lubed and move freely also check the throttle lock is not binding with the grip. Could also be IAC is sticking or needs replaceing

I have a 2008 Road King Classic with (the first year) TBW (Throttle By Wire - replacing throttle cables) and have no problems with it, and it doesn't do as yours does, but acts smoothly like a cable system.

My first suggestion is to take the twist grip off (you have to remove the master cylinder and switch housing) and check it's bore, and the handlebar end it rides on, for any built up crud (rust, dried up lube, etc.).

Sounds like the throttle lock is possibly binding up. Remove the right grip. There should be a little half moon shaped piece of plastic in there at the bottom of the switch housing. This plastic piece will have a small hole in the outside edge. This hole has to be placed over the pointed end of the throttle stop. The throttle stop is the plastic star wheel on the outside of the bottom of the right switch housing. There is a small metal Jesus clip on the inside of the switch housing. This clip is supposed to hold the stop from being turned completely out of the switch housing. It's possible the clip came off and is wedged in there.

they can stick in a number of places.
You may need to dissassemble the hand throttle assembly
Make sure the plastic twist grip turns freely on the handle bar.
Check the new grip doesnt push against the throttle switch assembly.
Check the cables move freely
Check the cables dont have any frayed ends
check the cables arnt missing any of the plastic outer cover
check the cables a routed correctly and dont get jammed or pulled turning lock to lock

Usually when you change the grips on the throttle side, depending on what type of replacement grips you bought, you'll be replacing the throttle sleeve as well. This means that you will be messing with the throttle and idle cables.

Loosen both cables at the adjusters as loose as they will go. Then, remove the two bolts that hold the right hand switch housing together. Carefully seperate the two halves. Do not damage the wires going to the switch. Work the throttle cable and the idle cable out of there slots in the throttle sleeve of the old grip. Be careful not to loose the brass ferrel that goes over the cable end. Lubricate the inside of the new throttle sleeve, the handlebar, and the area where the cables hook up with white lithium grease. Reassemble cables into new sleeve and reassemble the switch housing.

Once you have everything back together, adjust the throttle cable first and leave just a bit of slack in the cable. You should be able to freely "rock the throttle grip" before you feel the cable tighten up, Just a bit. Then adjust the idle cable about the same way.

Now, Turn the throttle cable to Wide Open throttle position and release it. It should "snap" shut, do this again from half and quarter throttle to make sure it works as it should. Failure to insure that the throttle operates properly can cause serious injury or death.

If you are simply replacing a grip on each side of the handlebar, use a long slender blade screwdriver or an ice pick to slide between the handlebar and the grip. Spray some WD40 in the work the grip a bit and it will break loose. Clean the throttle sleeve and handlebar off alcohol. Now, some people like to use "Grip Glue" on the new grips. Put the glue inside the grip and slide it up on the handlebar. If you put the glue on the handlebar, it will roll up in front of the grip as you slide it on to the handlebar or throttle sleeve. Make sure you "align" the two grips so they look the same before the glue sets.

Good Luck
Steve

Two things: First make sure there is some free play in the throttle cable. The twist grip should have a small amount of free-play, just a fraction of a turn, before the throttle actually begins to open. On the throttle cable, up near the handlebar, is a free-play adjuster.
Second, verify that the throttle cable is routed correctly. Confirm this by referring to the owner's manual for your Honda.
Both of these items are absolutely critical for correct and safe operation.

Remove the switch housing screws and spread it away. Loosen the adjuster locknuts on the throttle cables and adjust cables in, this will allow you to lift the cable off of the throttle grip. Be care full not to lose the barrels.( the small round caps on the end of the cable.) Assembly is the reverse. Make sure to check proper operation of the throttle before starting the bike.

I use hair spray. -Cut the old ones off -Soak the clip-on (left) w/hairspray -Quickly slide grip on and align. Once it is aligned allow it to dry. -Soak throttle tube (right) with hairspray, slid grip on, align, and allow to dry. I guess this is probably a bad time to tell you about the R1 throttle tube (or BRG throttle tube) mod. It's a bigger throttle tube which means less twisting to go WOT. Late model Gixxers are notorious for a long twist to go WOT.