Put An Aftermarket Seat On Stock Seat Rails

From mild to wild, the right seat can make a dramatic visual impact.

While most custom motorcycle builders will devote much of their time deciding on go-fast parts and paint schemes, the seat can play a huge role in adding more style to the finished motorcycle. Seat choices range from the sprung seats seen on many bobbers and choppers to a cafe racer’s race-bike-inspired humped seat. Since most aftermarket seats don’t include mounting hardware, you have to fabricate, weld or bolt brackets onto the motorcycle’s stock seat rails. Ultimately, how you mount your seat will mostly depend on the style of the seat, your motorcycle’s frame and your own abilities.

Instructions

Model-Specific Seats

1. Examine your motorcycle’s seat rails carefully to see how the stock seat was mounted. Most model-specific aftermarket seats are molded off the stock seat’s pan, making installation easier by providing an almost direct swap by reusing the stock mounting hardware (tang, latches etc.).

2. Check the positions of the mounting hardware on both seats to ensure that they are similar. If the seats are a complete match, bolt the hardware into place with a socket wrench. If some of the mounting points don’t match, create new mounting holes for the seat’s hardware with an electric drill.

3. Attach the seat to the motorcycle’s seat rails. Slip the seat’s tang into the slot on the motorcycle’s frame, normally found below the gas tank, then lower the seat onto the rails. Bolt the seat onto the frame’s mounting points with a socket wrench, or press the seat down to close the seat lock’s latch.

Universal Fiberglass Seats – Cafe Racer or Flat-Track Seats

4. Place a strip of 1/2-inch to 1-inch insulating weatherstripping along the underside of the seat to provide a cushion between the seat and the seat rails. Lay the new seat on top of the motorcycle’s seat rails. Look for strong areas on the frame, such as reinforced sections of tubing, to drill seat mount holes. You will need at least four mounting points, one at each corner, to provide the sturdiest foundation possible.

5. Drill directly through the seat and the frame rails at the selected points, using an electric drill. Remove the seat from the motorcycle.

6. Fasten the seat onto the motorcycle’s seat rails using a set of bolts, washers and nylon lock nuts. Place a washer near the bolt’s head to avoid cracking the fiberglass seat, then run the bolt through the seat rail. Slip another washer over the end of the bolt and loosely screw a nylon lock into place. Tighten the bolts and nuts completely once all four sets have been installed.

Bobber-Style Sprung Solo Seats

7. Place the seat’s hinged mounting bracket on the motorcycle’s seat rails near the gas tank. Check that there is enough room between the front of the seat and the gas tank to allow the seat to move without touching the tank.

8. Drill at least two holes through the mounting bracket and the seat rails with an electric drill, one on each side. Fasten the bracket onto the seat rails using a set of bolts, washers and nylon lock nuts. Place a washer near the bolt’s head, then run the bolt through the bracket and the seat rail. Slip another washer over the end of the bolt and loosely screw a nylon lock into place. Tighten the bolts and nuts completely once both sets have been installed. As an alternative, you can weld the seat’s bracket onto the frame.

9. Create posts for the seat’s springs, positioned on the back half of the seat, to prevent the springs from slipping off the seat rails. Mark where the springs make contact with the seat rails, using a permanent marker. Lift the seat away from the seat rails. Drill a hole through the marked areas with an electric drill. Insert a pair of longer bolts with washers through the bottom of the seat rails, then place a washer and a nylon lock nut over the end of the bolts. Lower the seat’s springs onto the exposed bolts.