The speedy cyclist who killed a pedestrian in Central Park last year gave his young son a lesson in bad biking on Wednesday — running a red light and riding on the sidewalk as his kid sat up at the handlebars.

Jason Marshall, 31, was seen by a Post reporter committing the two dangerous traffic infractions in East Harlem around 8 a.m. during the first five blocks of his ride from his East 120th Street building.

His son had a front-row seat for the risky ride, strapped to a $99 “Co-Rider” device with footholds and grips for his hands.

The saxophonist slowed down as he approached a red light on Park Avenue at East 118th Street — but blew through the signal rather than wait for it to turn green.

He continued three blocks down the busy street before veering onto the sidewalk, which he took for at least one block.[theplatform account=”4uMbOC” media=”media/guid/2389494712/2HMeyOLb7kK92IpJlgvR7FH1mDW56IWg” player=”Ud34RrXnH_qf”]

Marshall’s lawlessness comes eight months after his deadly ride in Central Park.

On Sept. 18, he slammed his $4,000 Jamis Eclipse bicycle into Jill Tarlov, 59, along West Drive.

The wife of a CBS executive was left brain-dead from the crash and died three days later. She’d been visiting the city from her home in Connecticut to shop for her daughter’s birthday present.

Just before the collision, Marshall was seen racing downhill in a lane restricted to pedestrians and child bicyclists, law enforcement sources have said.

Marshall dismissed the crash as an “unavoidable accident” and told cops he was traveling just 8 or 9 mph — although witnesses claimed he was pedaling at three times that speed.

He was never criminally charged.

Prior to that crash, the musician boasted of his breakneck speeds on the website Strava.com. One of his posts had his speed at more than 35 mph, far faster than Central Park’s 25-mph speed limit.

During Wednesday’s ride, Marshall and his son were on an $1,800 Cannondale bicycle fittingly called Bad Boy.

Police sources said Marshall would have been issued a summons and faced a fine of $50 to $75 for the red-light violation if it had been observed by a police officer.

He could have gotten a criminal summons for pedaling on the sidewalk, requiring him to show up in court.

When asked about his law-breaking bike ride, Marshall said, “I don’t know. I had nothing to do with any of that. I’m sorry.”

A receptionist at the law firm representing him in the fatal crash declined to comment.

Tarlov’s husband, Mike Wittman, did not return calls for comment.

Additional reporting by Shawn Cohen, Frank Rosario and Danika Fears