York Recorder Judge Sean Morris directed the jury at York District Court to return not guilty verdicts on both charges facing 28-year-old Luke David Jackson.
He ruled that there was insufficient evidence for the jury to return any different verdict.
Mr Jackson, 28, of Jute Road, Acomb, denied charges of robbery and carrying a knife in public.
The judge issued his order after hearing briefs from the prosecution and defense attorneys, initially after the prosecution had closed its case.
He ruled at the time that there was not enough evidence to convince a jury that Mr. Jackson was the masked biker who threatened a father and his son on Front Street.
Mr. Jackson denied being a man, and neither father nor son identified him as male.
Following the defense, the prosecution and defense attorneys again discussed the legal issues surrounding the robbery charge. It is linked to an incident where a masked cyclist grabbed money from a till at Costcutters in Wains Grove, Dringhouses.
Mr Jackson denied being the man and said he had not been in the store that day and did not generally shop there. The saleswoman did not recognize him as a robber.
The judge then ruled that there was insufficient evidence for a jury to convict Mr. Jackson on either charge.
Mr. Jackson was formally acquitted of both charges.