The motorcycle minigame is right at the start of chapter 4, so if you miss this during your first playthrough you can come back to it via chapter select in easy difficulty.
There are two halves to this minigame. In the first half you will be in the tunnel and will have 3 different types of enemies to fight.Highway Patrol Bikes
: These will shoot at you or attack you with melee weapons but are fairly easy to take down. Three hits with a sword or a single hit with the Sharp gust ranged attack will defeat them.Shinra Military Bikes
: Tougher to take down as they will take more damage before going down. They will also drop molotovs which you will need to dodge to avoid taking damage.Slug-Ray drones
: Will come flying in and deal AOE shock damage. They will also target you directly so dodge when you targeting laser shows up. They don't take much to take down but try to get to them between attacks.
Your sharp gust ranged attack will hit multiple enemies, so if you line them up right you can take down or damage multiple enemies in a single hit.
The second half is outside of the tunnel and after you take a few bikes down will only leave you with one enemy, Roche the SOLDIER. He has several types of attack.
He will pull forward and send two types of ranged attacks backwards. For both you will want to dodge left and right but also block to minimise damage if you do get hit.
When you're fighting him, he'll sometimes pull forwards and slam his back wheel down at you and you'll want to avoid that.
He will also drive up on the wall and fire lightning bolts down which you can mostly avoid by zig-zagging in advance.
When coming off the wall he'll slam down with AOE damage.
When you're attacking him up close his sword will glow blue and he'll perform a heavy attack, so move away from him.
The fight is fairly straightforward. You'll need to look out for the signs of his different attacks and avoid accordingly then, whenever you can, get up close and hack away with your sword. The Spinning Slash attack will deal him a lot of damage if you're right next to him so use that.
Below is a video of the whole minigame in easy difficulty.