Comfortable motorbike riding requires a good seat, but buying a new motorbike seat can become expensive quickly, especially if you want any customisation done on it. Luckily fabricating a foam motorbike seat does not require much in the way of special knowledge or expensive tools. Fabric shops and craft shops carry most of the supplies you will need, and frequently run sales where the foam and seat coverings cost even less than usual.
Remove the covering from seat. If you are working with a seat that already has a cover, remove the cover and inspect the current foam. You have a choice of replacing the foam entirely, or adding new foam to what already exists to create a more supportive seat. If you wish to start from scratch, remove the existing foam from the seat pan.
Install foam block. If you are starting from scratch with the foam, shape the bottom of a block of the high density foam with an electric knife so that it will make as much contact as possible with the seat pan. Once the bottom of the block has close contact, spray adhesive both on the seat pan and on the block to adhere the block to the pan.
Shape the foam. Whether you are using some existing foam or starting new, the foam needs shaping into the desired fit. On a block of new foam first cut a general seat shape with the electric knife. Sit on the seat and feel where it needs more support and where it has lumps that create discomfort. Remove the lumps with an electric knife or file. Add additional foam where the seat needs more support by using spray adhesive to glue additional pieces of foam to the main block. Continue this process until the seat feels right.
Once the foam is shaped to a good fit for the rider, cover the seat with leather, vinyl, or other durable material. You can use the original covering as a template, or you can make your own pattern by tracing the seat shape onto inexpensive fabric and leaving enough room so it will fit under the seat. Align the covering over the seat and staple it into place starting at the front of the seat and working your way around each side to the back. You can also take the seat into an upholstery workshop and have it professionally recovered.
When you test the seat make sure to sit in the position you would sit in while riding. A seat may feel fine while one foot is down, but have uncomfortable spots when you sit back as if you were going down the road. An optional addition of memory foam or a gel pad can make a seat even more comfortable. If you choose to use a comfort pad, carve a space for it into the seat foam and inset the foam or gel pad into the seat.