The goals for this project were:
*Make a seat for my Honda 100 out of material that I had lying around
*Have this seat be comfortable enough for rock and roll
*Have the seat look "professional" enough to be proud of
*Be easily removable
*And, most important, have the default position for my butt be almost a foot behind where the stock seat puts you.
I succeeded in these goals. At this point, this is an interim seat while I finish customizing the bike. I suspect that I will want to add more padding at some point (simply a matter of cutting the tape, laying a couple more layers of pad, and retaping). When I put a more classic tank on the bike, things will look less... jury-rigged. As it is, I kind of fancy it a "junior streetfighter" look without the side covers. I also enjoy not burning my leg, so the covers get put back.
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Step 1: Remove Your Old Seat
Don't do this during a short break in a rainstorm. You might think the rain is over, but it will start up again at the most inopportune time and you'll have to ride your bike back to the shed, in the soaking rain, with no seat. Not only is this unpopular with your tailbone, but I can assure you that you will slide off the slick framerails at least once. Fun.
Okay, got your bike out of the shed and into your workspace? Go get your socket set and an extension. A perisope attachment for your neck will also come in handy.
All the fasteners you will be cussing at measure 10mm for a Honda 100.
See those bolts? Yes, those, ungodly far from any human access? Remove them. These hold your back fender on. Removal of the fender isn't required, but it helps later, trust me.
Step 2: Remove the Side Covers
These hide the only two mounting bolts for the whole seat. Leave these off for a "junior stretfighter" look, or put them back on at the first opportunity, which will be after you have made and mounted your new seat. Until then, keep track of all the bolts and washers.
Step 3: Finally Get That Seat Off
This requires an interesting motion. Remove the two mounting bolts, then push down on the lowest part of the seat, near the front. Use the other hand and grab the tail of the seat and pull back/upwards. You have to keep the nose of the seat pinned while you rotate the back end in an upward arc, and the seat will come off.
You can see here how the seat and tank are mounted. A rather ingenious setup, but a pain to work with "blind". Once you've seen it, things go back together easier.
Step 4: Sit
The stock seat was several inches thick. Your new seat won't be. Figure out where the best place is for your hind end by sitting on the bike. Complicate this with a 3-second self-timer for the photos. Having fun yet?
Go ahead and try a couple of laps of your yard (an obstacle course to rival the endorsement test) in various positions if you like, but let me warn you that the framerails have the friction coefficient of Teflon-coated ice, especially in corners where you really need to stay on the bike. Slide off the rails for the second time in two days. Run over your own foot. Ride back to your work area. Go get ice for your groin.
In fact, while you're at it, go grab a Sharpie and some cardboard, too.
Step 5: Make a Template
This seat design uses plywood. Many thanks to Skunkbait for that one, you saved me a lot of work! I would not have thought to use plywood, but it works quite well, is plentiful, and requires very little special ability.
First, figure out how you're going to mount your seat. I can practically guarantee you that the stock mounting points will no longer work. Sure, you could bodge together something, but why do that when you've got all these wonderful holes right under where the seat is going to go?
Because plywood is flat and motorcycle frames aren't I had to use the holes right up by the tank and back next to the fender mounts in order to get two sets of mounting points. Pity those wonderfully laid-out center holes can't be used, but oh well.
Place your cardboard on the frame and trace the shape of the frame onto it from underneath. Cut this out and check the match. Mark your mounting holes from underneath and cut these out.
Step 6: Mark Your Cut and Cut Your Pan
Grab your jigsaw and a woodcutting blade.
Trace your template onto your plywood, including your mounting holes. Cut out the outline, but don't drill the holes unless you will actually be using them to mount your seat.
It was at this point that I scrapped my original plan of putting carriage bolts throught the seat and threading nuts on from the other side. If you stop and think about it and notice that you don't want to cram your hand under there, either, let alone try and tighten nuts that way, you'll scrap the bolt idea.
Of course, if you want a more permanent seat installation and your frame of choice allows you to access fasteners in the appropriate locations, drill your holes and put your bolts in now.
Step 7: Add Pad
I used carpet padding. We have way too much of the stuff, and rather than watch it become a condo for more spiders, I figured I'd use some of the excess. I could have grabbed more foam, but I figured ol' ironbum would be fine with a little more than one layer. I was wrong. Use at least two full layers.
Cut your pad to roughly fit your seat, with overhang on all the sides possible. Sharp corners to the inside of the thigh aren't fun. You want to pad those.
I stapled my foam to the plywood in the back to hold it roughly in place while I taped. Don't count on stapling everywhere with your handheld staple gun. Since you are going to be brighter than I was and use two full layers, you will need to glue your second layer to your first. Then cut two strips of pad as long as your seat and about two inches wide. These will go on either edge to help ensure you don't feel that sharp plywood edge. Ideally, they should cover the corner and extend far enough in so that your hipbones sit on them. Trust me on this, you want the bit your hipbones rest on to be higher than your tailbone's resting place.
You can just set these strips in place.
Step 8: Upholster
Run a strip of your duct tape lengthwise. Make it taut. Run a widthwise strip to trap your foam and strips in their proper places. Make this taut also.
Don't use Gorilla Tape, use regular old duct tape. It has plenty of sticking power for this job. If you just tried to tape widthwise with Gorilla, you just learned why I say don't use it for this. Way too much sticking power. Since we're using the weak stuff, make sure you stick the tape to itself every time you wrap a strip of it. Sticking it to anything else won't work so good.
Continue your upholstering, working outward on each side of this center strip. Pull the tape taut, and make sure to overlap a little bit. Once you get the foam all covered in the narrow axis, make some longer strips to cover the back end. These need not wrap all the way around, but do make sure both ends are getting stuck to tape, not foam or wood. Pull these extra taut.
Finish the seat covering by wrapping some tape around the nose of the seat. In my case, there's no padding there. This is partly because of the physical limitations of my spare foam, and partially because I didn't want to encourage any part of my body to occupy that space.
Looks pretty sharp, don't it?
Step 9: Mount
If you're going for a quick-detach seat like I was, you'll be using five nails as locating pins. Place the seat in the proper position on the bike (sit on it to make sure... maybe even take a tentative lap) and reach underneath with a nail. Mark the locations for your pins one at a time by pressing the nail into the tape, in such a way that the seat can be installed and removed easily, but with minimal other movement once it's installed.
Some movement is unavoidable, but not an issue once you have your weight on the seat.
Step 10: Conclusions and Thanks
Thank you so much to Skunkbait for suggesting a simple plywood pan, rather than letting me overengineer something crazy. Building my own "semi-bench" seat was quite fun, and I know what I'd do better the next time around. This one here is definitely a solo saddle... for now.
I'd like to tackle more seatmaking projects in this vein. It's a nice change of pace from my usual seat design, which is closer to a tractor seat than anything else, and made of different materials.
As for riding, the seat rides great, but you have to be a bit careful when kickstarting that you don't clip the edge of the seat on your way up and knock things off kilter. The tape has a good amount of grip (no more sliding off sideways!), and it is easy and comfortable to sit in the right position.
Overall I'm proud of how well things turned out. Black duct tape makes for an excellent seat covering when you have nothing else. It's an extremely versatile medium.
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