Some have found that the throttle sleeve is sticking mostly after a grip replacement.
On the cable drive throttles, a lubrication of the bar where the sleeve rotates will return it to new again. I use Bike Aid also known as dri slide for this, it works well and the throttle sleeve rotates nice and smooth.
While you are in there do the throttle cable lubrication also on both cables. The bike aid comes with a needle tip dispenser that makes it a very easy job and nothing has to come apart to do it.
Available here Iron Braid - Product Index
On the fly by wire bikes, the cause is usually a grip that is too tight on the bars or too far onto the bar. It can be remedied by loosening up the clamp screws that attach the throttle assembly on the bars with a #25 torx or allen depending on which you have and backing off the assembly just a bit (1/8") or so until it rotates freely.
On the cable drive throttles, a lubrication of the bar where the sleeve rotates will return it to new again. I use Bike Aid also known as dri slide for this, it works well and the throttle sleeve rotates nice and smooth.
While you are in there do the throttle cable lubrication also on both cables. The bike aid comes with a needle tip dispenser that makes it a very easy job and nothing has to come apart to do it.
Available here Iron Braid - Product Index
On the fly by wire bikes, the cause is usually a grip that is too tight on the bars or too far onto the bar. It can be remedied by loosening up the clamp screws that attach the throttle assembly on the bars with a #25 torx or allen depending on which you have and backing off the assembly just a bit (1/8") or so until it rotates freely.