An LED H4 is compatible in the sense they correctly plug into the keyed H4 opening on the back of the headlight housing. However the bike has a rubber dust cover that fits over the base of the installed bulb and I have never been sure it would fit/seal over an LED H4. It's a confusing issue since the back end of an LED H4 extends much further back than a halogen bulb plus different models have widely varying shapes there, even built-in fans, all due to the need to dissipate the heat of the LED.
Hopefully someone who has tried one will post.
If you do go with an LED, keep in mind that the down-the-road shape of the low beam depends on the LED's being in the exact same location as the tiny coiled low-beam filament of a halogen bulb. Cheap LED bulbs use LED's much larger than that, the laws of optics say the resulting beam will spread out much more, including into the eyes of on-coming drivers. Best ones I've seen use 3 very tiny LED's in a line to match the rectangular shape and size of the filament.
You can find comparison reviews on YouTube with actual testing of the beam shape and brightness.