American Chopper: Senior vs. Junior - Season 4

Senior proposes that he and Junior combine forces to build a bike, but Junior is unsure of how to respond. When Rick's wedding brings the two together, Junior gets the reassurance to make a decision once and for all.

Senior and Junior brainstorm bike styles for their upcoming collaboration and decide to recreate the first bike they ever built together. PJD unveils the Geico Armed Forces tribute bike and OCC reveals the Café bike at the opening of OCC Café.

Senior and Junior get to work on their big bike build, which reaps surprising results as the two bond over old memories. Meanwhile, PJD starts a trike for Loopster while OCC builds a bike to benefit Senior's favorite charity.

Brought together by a father-son bike build, Junior and Senior begin to open up. While their relationship grows away from the shop, OCC starts a bike for Wildgame Innovations and PJD unveils a five-wheeled trike for Loopster.

PJD starts a build for technology company QUBX while OCC assembles and unveils a bike for Wildgame Innovations. Meanwhile, father and son continue their collaboration on a re-vamped version of an old school bike.

OCC starts a build for Sturgis, PJD unveils a high-tech bike for QUBX and the Teutuls finish their father-son build. Later, Junior and Senior take their new bike for a ride and Junior has a big surprise for his dad.

Senior receives a stern, on-air lecture from a late night celebrity, Junior launches a new business venture and Senior visits PJD for the first time ever. Then, at Sturgis, Senior rides side by side with a bike industry icon.

Junior visits OCC and brainstorms with Senior about potential future collaborations including creating a production line of bikes. Meanwhile, PJD finishes a bike for RoadLoK while OCC starts a SuperBike build.

Senior and Junior start brainstorming the production bike, but the road is rocky from the start. First, the two bump heads when discussing design workflow. Then, when Junior leaves town, Senior hijacks control of the project.

With the Teutul's new company seemingly at a standstill, Senior takes steps to initiate progress, sans Junior's approval. Mikey provides much needed help to his busy brother, and PJD and OCC both stage unprecedented unveils.

Senior throws down the gauntlet for a build-off rematch. The stakes are raised when a new player is added to the mix. Back at OCC, tensions rise around the lift when Jr. and Sr. disagree on the production bike design process.

When hurricane Sandy hits, the PJD crew rushes off to rescue the 9/11 Memorial bike. Progress on the production bike stalls out when Sr. and Jr. disagree on a plan of action. Sr. and Vinnie finally face off about their past differences after 5 years.

PJD's 911 Memorial Bike is in more hot water than they thought. The pranks leading up to Chopper Live rev up and Sr. and Jr. hit a snag when the production bike discussions open old wounds.

In the series finale, the crews are under pressure to finish the 911, GAF and Venetian bikes. Cody goes after OCC with a revengeful prank as Chopper Live draws near. Sr and Jr find common ground in their relationship.

Senior, Junior and Mikey make a lasting impression by donating the TEUTUL Bike. Senior pulls one last prank and the threesome takes a raucous ride through the most dramatic and defining moments of American Chopper.