Reshaping a Ninja 250 seat - the story

Posted July 12, 2004

You may also be interested in the how-to on reshaping your seat.

The Kawasaki Ninja 250 (aka EX250) comes with a very oddly shaped seat, designed for no one in particular. I rode mine with the stock seat for about a year, and found it to be comfortable enough for daily commuting work, but awful when riding for more than about an hour. In particular I took a ride with some other Ninja 250 riders, and by the end of that, my butt was in awful pain. I resolved to do something to fix it.

The Plan

What I decided to do was procure a used seat, and add foam to it. This would then be cut down to the appropriate shape, covered with headliner foam, and then covered with vinyl. A simple enough plan. I wanted to move the seating position back and up, since the stock seat has me sitting uncomfortably forward and down, cramping my legs and making the bike at best a short-term ride.

I had seen how a Rich's custom seat is made, so I had a good idea how to go about the process myself. That's where I figured out what kind of foam to use, what shape to make, roughly the order of events, etc.

Procuring the Pieces

I found the seat on Ebay, for about $40 shipped. I located the foam at a local foam shop for $25 (enough for two tries), and the headliner and vinyl at a local auto upholstery shop for a total of about $30. I also got foam adhesive at the foam shop, for about $10 (although I ended up needing a total of 2.25 cans -- see below).

Specifically, I got "5lb rebond" as the main seat foam: this stuff is formulated out of scraps of other foam, and is much stiffer than most commercially available "pure" foam. If you're reading this article with an eye toward doing it yourself, make sure you get rebond foam. It turns out Rich's uses 4lb rebond, and indeed, I think I would have preferred that for my main seat foam, as it's a bit softer while still being stiff enough.

The Process

The way I did it is like this, in concept. Of course in reality it's more complex, but these are the basic steps:

1. Remove the old cover from the seat, and discard it
2. Spray old seat foam with adhesive, allow to sit for 30 seconds
3. Spray new foam with adhesive, let sit for 30 seconds
4. Carefully lay new foam on the seat, pressing to get good adhesion
5. Using an electric carving knife, cut out the basic shape
6. Using a small ~40 grit grinding wheel, finish the shape
7. Ride the bike with the "finish-shaped" seat, and regrind until it's right
8. Spray finished seat with adhesive and let sit
9. Spray headliner foam with adhesive and let sit
10. Carefully lay down headliner on seat, avoiding wrinkles and air pockets
11. Spray concave areas of the seat with adhesive, to stick down the vinyl cover (otherwise it bags out and looks cheap)
12. Stick on the vinyl, and stretch and staple it to the seat pan

And Then Reality Intervened

Everything did not go as smoothly as I would have hoped. My first failing was that I was trying to do the whole job with just the electric knife. The knife is good for removing large chunks of foam and getting the rough shape, but is terrible for fine trimming. I spent a good several weeks of intermittent work with the knife, trying to get the shape right, riding the bike to work and back, and going at it with the knife again. Do not bother trying to do this, it's terribly frustrating and ultimately led to me giving up on the seat for a few weeks.

I dropped into Rich's to ask his advice, and basically he said, "you're on the right track, now finish the shape with a small grinding wheel." He said a lot more than that, because Rich is a talker, but that was the gist of the seat advice.

I got a set of 3" griding wheels from Sears, and suddenly things were going well again. Using the grinding wheel allowed me to make the smooth, flowing shapes I wanted, and get the really concave shapes that were impossible with the knife. It took some getting used to, but I was able to progress from a shoddy-looking, scrappy seat to a smooth one in just a few days of after-the-workday work.

The final challenge that I hadn't anticipated was that getting the final shape right took a lot more futzing than I had expected. I spent at least a month, maybe two, of occasional work with the grinding wheel trying to get the final shape right. In the intervening time, I'd re-applied foam twice so I wouldn't be working on the old, troublesome shape. I ran entirely through 1.25 cans of adhesive (the first can I bought was a quarter-full can that the guy at the foam shop sold to me for $4) in getting the shape right, and had to go buy a third can to finish up.

How to Make Progress: Get Frustrated

The final burst of activity on the seat occurred not because I'd gotten the shape perfect, but because I got it good enough. I ground out the last little problem area that was still really noticable, and decided that was good enough. I applied the headliner material, and stretched on the vinyl.

The final product wasn't perfect, with slight bagginess on the sides, but it was pretty good. I now have a seat which is much more butt-shaped, and thus more comfortable. The seating position is at least 4 inches further back than the stock seat, and at least 2 inches higher. This makes my legs more comfortable, but means that my arms are stretched a bit too far, and throws off the balance of the bike a little bit. It's still a huge change from the banana-seat supplied with the bike.

Final Product: Good, Took Forever

In all, it took me 3 months from buying the spare seat on Ebay to getting the custom seat finished. Most of that time was passed doing nothing to the seat because my schedule got busy, or when it was raining out (and thus I couldn't test ride any changes since the foam would get soaked).

I'm actually thinking about doing it all again, and moving the seating position further forward while keeping all the height (possibly adding even more). I also have a much better idea what I'm doing now, and think I could make a nicer looking seat in much less time.

Created by Ian Johnston. Questions? Please mail me at reaper at obairlann dot net.