[vveva]

Man travels back in time on motor bike and becomes his own great grandfather when he gets back to present time?

[Wondergirl]

Is it this?

Timerider: The Adventure of Lyle Swann (1982) - IMDb

Plot

Lyle Swan (Fred Ward) is a well-known dirt bike racer who is in the desert competing in the Baja 1000, a multiclass vehicle cross-country race. Swann has a reputation for being a great rider, but plagued by technical problems from the high-tech gadgetry he incorporates into his Yamaha XT500 motorcycle thumper. When Swann accidentally goes miles off course he stumbles across a time travel experiment that utilizes "maser velocity acceleration" to send objects (in this case, a simian subject by the name of Ester G) back in time. Swann rides through the field and gets sent back to November 5, 1877 but rides off moments before the system can return him to the present. Unaware of what has really happened to him, Swann rides off towards what he thinks is civilization. He soon comes across the small California village of San Marcos, but his red suit and dirt bike scare the local Mexicans, who think he is the Devil.

Swann meets a beautiful woman, Claire Cygne (Belinda Bauer), and sleeps with her, but she is later kidnapped by a ruthless outlaw, Porter Reese (Peter Coyote) and his gang of rapists, thieves, and murderers. They also manage to capture Lyle Swann's dirt bike, leading to a series of hijinks, while Swann gets help from a posse trying to capture or kill the gang.

In a final showdown, Reese and Swann face each other atop a plateau. Just as a helicopter shows up (sent by the builders of the time travel experiment) to take Swann home, his dirt bike falls off the side of the plateau, distracting Reese, who gets mangled by the helicopter's tail rotor, leaving only a pair of bloody boots behind. Just as the helicopter pulls away, Claire snatches from Swann's neck a pendant handed down from his great-great-grandfather…and he realizes that he is his own great-great-grandfather.

[vveva]

Yes, thank ever so much...

[gmdogg]

My Own Grampa