Someone's messing with Jaleel White's prized possessions -- 2 top dollar electric bikes were burglarized from his home ... and you better believe Urkel's pissed.
Law enforcement sources tell TMZ ... Jaleel discovered one of his garage doors was left unlocked Thursday afternoon, and a thief had made off with his Stromer electric mountain bikes.
Jaleel tells us one of his alert neighbors -- who was aware of the burglary -- saw a guy riding around on the bike not too far from Jaleel's home. The neighbor snapped this pic, and Jaleel tells us he's given it to cops. We're told they're now investigating.
This much we know ... whoever jacked Jaleel's rides must not know what he does to thieves who mess with him.