Making A Custom Seat
...a very quick tutorial based on the Husqvarna build.
Have a general idea of what you want to do. Admittedly the below sketch is too thin for comfort so I'll be beefing it up some.
Make a seat pan. You can use aluminum, stainless steel or mild steel. If you use mild you'll need to powdercoat it (like I did). 16G is a good steel thickness. You may want to use a 14G for aluminum. Do not paint it. Most professional upholstery glues will eat through paint.
Go to your local upholsterer and test out some seat foam densities. Buy a roll of it (around $75 for 6'). Also pick up an electric carving knife. Get a nice one. The one shown here was only $20 and it burnt out within the first 10 min. You're going to put a lot of load on the motor cutting through dense foam.
Cut out a rough shape, leaving some overlap off the edge of the pan. Use a spray adhesive to attach the foam to the seat pan.
Layer up the foam as thick as you want, using the spray adhesive to bond them together. I went with 2 slabs of 1.5" foam. After you get your cake layered use the carving knife to trace the shape of the pan, cutting off the excess.
Put the stack up on the bike and test the comfort. Remember you'll be taking material off so if you're on the fence about it's comfort now definitely add more foam. You shouldn't be able to feel the seat pan if you bounce up and down on it. Depending on the kind of seat you're after this is also a good time to grab a Sharpie and mark where you land on the foam. You can use these marks later to draw out contour lines to follow when you start carving.
Measure and draw in your guidelines with the Sharpie. Try to get your lines as symmetrical as possible before carving. Going at it freehand will likely cause you to take off more material than desired as you go from side to side trying to get them even.
*Note - mines's looking a little chunkier than desired since my knife died on me halfway through. I ended up buying a new one and smoothing it out further from here. You can also use a vertical belt sander to smooth it out.
Make sure you keep testing it throughout the process to assure you're not taking too much off.
If you want crisp edges keep them sharp in the foam. When the upholstery is stretched over the form it will round them off quite a bit. For the upholsterer you can either draw up a stitching diagram of the seat or draw out your stitch lines right on the foam. Head over there, pick out some materials and throw your money down.
Vinyls are much more water resistant than leathers and look identical. Downside being the leathers wear in nicer and can be conditioned. Vinyls can be prone to creasing and cracking over time. The CX500 seat is vinyl. It's been on there for about 6 years now and just started cracking this summer. I probably put a couple thousand miles on it a season.
Here's how the Husqvarna seat turned out. Black alcantara on black vinyl with a champagne stitch. If you're looking for a tuck and roll the upholsterer will lay down a 1/4"-1/2" layer of low density foam on top to give it the depth. Below is 1/4". Go for the 1/2" if you want it deep enough to hide the stitch. Vinyls will give more definition than leathers due to their stretch.
...back to finishing the rest of the bike.