Their rocky road to an on-air reconciliation is captured in a new “American Chopper” special airing Tuesday, June 9 on Discovery Channel at 9 p.m. In the two-hour telecast, they return to where it all started back in 2003: the original Orange County Choppers building in Newburgh, NY, which is being torn down.

There, they reminisce, bicker and, ultimately, build a custom bike for ABC Supply Company.

“I was pushing for this for a long time,” Paul Jr., 45, tells The Post. “My father wasn’t really interested for his own reasons, but nobody is getting any younger. It’s been over 10 years and I just thought I would like to build a bike with my father again, if we could.

“We shared so much in the early days and made history with [‘American Chopper’] and we started in that building,” he says. “It made me think back to a time when my career was being formed through the process of being given the opportunity to build bikes … we fought and got along, too –and  it took both of us to make [the show] as unique as it was.

“It was a big trip, and a good one, down memory lane.”

Paul Sr. famously fired his son from the family business in September 2008 after a huge blowout and they went their separate ways. In 2009, Jr. opened Paul Jr. Designs (PJD) in Montgomery, about 20 minutes from Orange County Choppers.

He married wife Rachael in 2010 (Sr. was invited to the wedding but did not attend) and their son, Hudson, was born in February 2015.

“When you become a father it makes a difference in the way you see your own father,” he says. “It changed my viewpoint [toward Sr.] in some degree — it would be hard not to. I started to switch things around a little; I always wanted to get into a good situation with my father. You can do forgiveness on your own — the thing with reconciliation is that it takes two.

“And that’s always a challenge.”

Jr. says that, while building the bike with Sr., some of the old tensions resurfaced.

“It was up to me to step aside and refocus on what I wanted to see happen in this scenario, like what was important about the build,” he says. “There were some creative differences. I’m a very passionate, creative guy, so there was that clash-y thread and we certainly had some heated moments. It’s been over 10 years since we verbally had an argument with each other.

“I thought, ‘You know what? I don’t care if we’re building a widget together, the important thing is to work with my father again.’ I had to swallow some pride and get into the position of, ‘This is about me being a dad and building a bike and not getting sidetracked.’ I’m not going to lie to you. It was challenging, and I’m sure my father would agree.

“But ultimately it worked out.”

Jr. says he and Sr. haven’t had much contact outside of the television cameras.

“We speak occasionally and we text,” he says. “He’s [living] part-time in Florida. I’d be lying if I said we were best friends. It just hasn’t worked out that way and it’s not what I prefer but we’re not dealing with a perfect scenario.”

Despite that, he says we might not have seen the last of Sr. and Jr. collaborating on a bike build.

“I would like to do more with it,” he says. “My intention is maybe to do another project [with Sr.] or multiple projects. Life is short — what can we do to make things good inside the family and get together?