Most modern motorcycle manufacturers transitioned their lighting systems to the new digital format which includes the use of low current LEDs.
However, before this digital conversion revolution, mororcycles were built using an analog system that isn't immediately compatible with LEDs. This means that when installing digital LEDs on these older bikes issues may arise and your new LEDs may not work as expected.
Symptoms of an incompatible LED turn signal installation include lights that blink too quickly (hyper-flashing) or the lights don't not blink at all. The reason this happens is that the current draw for LEDs is much smaller than that of an incandescent bulb. The bike's analog flasher relay interprets this as a burnt out or missing bulb and reacts as it was designed to in these situations.
The good news is that these issues can be easily resolved at reasonably low costs. Nowdays, there is a long list of plug-and-play connectors on the market designed specifically to integrate LED lighting systems with old style (analog) motorcycles. They are frequently referred to as Load Equalizers or Digital Flash Relays.
Some manufacturers build theirs to fit specific motorcycles, while others offer more generic systems. Regardless of their composition, they all pretty much perform the same function which is to correctly regulate the flash rate of your turn signal.
Here are two equalizer examples (plug-and-play and generic). Of course this is not a complete list, but should give you a starting point when searching for the right component for your bike. For more information about each type tap on the images below.
Badlands M/C Products Load Equalizer III LE-03-SR
Plug-and-play. Fits 2010-2013 Street Glides and Road Glides only
Badlands M/C Products Load Equalizer LE-01
Generic version. Fits all vehicle types. Wire splicing may be required.