Janko's rasping first-half volley was incorrectly ruled out for offside, a decision that incensed the home side, who are now seven games without a win and will wonder what could have been.
Sydney goalkeeper Vedran Janjetovic was rarely called upon in the first 55 minutes, but a sloppy error from him almost presented the visitors with a simple goal.
Janjetovic looked like he would claim a David Carney corner easily, but the ball slipped through his hands to give Adrian Madaschi a glorious chance to score.
The defender nodded the ball towards goal from just six yards out, but Sydney skipper Alex Brosque was back on the line to head it clear.
The draw means the Jets, who are second bottom, avoided a third successive defeat.
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