Thursday, August 1, 2013

Cutting the Seat, Lowering the Bike: KTM 350 EXC-F



One of the best ways to lower the height of a motorcycle is to cut the seat. It's cheap, fairly easy if you are patient and even if you blow it it's not to expensive to fix (on my KTM a new replacement seat is about $100).

I have pretty short legs (a 28" inseam) so I decided to cut the seat on my KTM as low as it could go. Obviously, you can cut your seat much less than this.

What do you need
- a pneumatic staple gun. You can't do this with a hand held stapler, don't even try. Alternatively, you can do everything else, and then bring the seat to your local upholstery shop and ask them to staple the cover on for you. I've done this and its very quick and easy for a pro, maybe 15 minutes!
- stainless steel staples (no rusting!) I use 1/4 deep. You want them short so they don't go through the foam.
- a LONG bread knife. The longer the better. I use a 10" one.
- a Surform flat file. Get one, it's worth it. I've heard guys do the final shaping with sand paper... that must take forever! The Surform makes it easy.
- a vacuum cleaner to clean up all the foam bits and dust
- a day without wind (or a well lit garage)

Step one: Photos
Take pictures of your existing seat for reverence. Particularly take shots of the existing staple work so you can reference them when you put your staple on. The bottom of most seats is irregular, and seeing how the factory placed the staples can help.

Step Two: Cover Removal
Remove the existing cover. In some cases you might not have to take it all the way off, like if you only want to trim the front of the seat. I use a pic to pry the staples up:

And then pliers to pull the staples out:

Step Three: Marking the Seat
This is the important part to get right. Mark a line down the middle of the seat from front to back with a fine point sharpie (felt tip pen).  Then mark a cut line on both sides of the seat. Measure down from the center line to be sure the lines on both side are symmetrical.  You can see I have all sorts of marks that I used to make my measurements. The black line is the "cut line" is where I want to cut. It is important to make another line a "reference line" (I used red) a bit below the cut line! Because after you cut and file a bit, your cut line will be gone, the red line below serves as a reference after the cut line is obliterated. (I learned to do this the hard way.)
You need to be very careful to look at the underside of the seat and to be sure you leave enough foam to protect your butt from the seat pan. This is the time to inspect, measure and mark carefully. And then to check it all twice more.

Step Four: Cover the Bike
Cover the bike and put the seat back on. I've done this without covering the bike and foam got everywhere... not good as you don't want foam bits to melt onto hot parts of your bike next time you run it. Cover the bike to prevent this problem. Also, do this on a day without any wind, otherwise the foam filings will blow everywhere!

Step Five: Cut!
Cut the seat. The picture below is from cutting my old Husky. Getting started can be hard, especially with a thin cut. It might be better to make the first cut in the middle where it is thickest. A long knife allows you to hold both ends and watch the cuts on both sides of the bike. An assistant can be helpful with this too... my wife was kind enough to watch the far side and warn me if I was heading off course. You really need a knife longer than the cut you are making. Note on this cut on the Husky seat I don't have the extra red line for a reference. It would have been easier with that.

Here is the slice I took out of the KTM seat. You can see I started in the middle where it was a thick cut  and did the front part and then I cut the rear. Frankly, it's easier to make a big cut like thin than a thin one! It's like cutting soft bread!

Step Six: File or Sand

This is a great shot. This is right as I started filing with the Surform. You can see the uneven cut marks from the bread knife. You can also see the red marking line that will help me keep the seat even after the other black line has been obliterated.

And here is the seat after I finished filing the flat top. You can see it's smooth but not perfect. Small imperfections will be invisible when you pull the seat cover tight over the foam.  Get the seat as good as you can but don't worry any small stuff.

The original KTM seat has a bevel, it's not a flat top like above. So I drew a new center line and two other lines parallel to it to mark where the bevel would end. I wanted the bevel to end crisply on the top. Some people might prefer it to be rounded but this was my choice. I also added some marks for the bottom edge of the bevel, but they aren't in this photo.

Here is a picture of me making the final bevel with the Surform file. I use the Surform to do all the final touches.

 Step Seven: Covering
I use a layer of thin plastic wrap from the kitchen over the seat. I'm not sure this is necessary, but I'm a bit concerned the raw seat from the cutting might be more likely to absorb water. Hopefully this thin plastic layer would prevent that. You can also see the sharp edges I made on the bevel and the remnants of the pen marks I made to guide that filing.
And here is a shot of the scotch tape I used to hold the plastic wrap in place while I covered the seat.

Now it's a time to stretch the cover on.  You saw earlier I removed a lot from this seat, so I had to work stretch the cover tight  Fit the ends over first and put a few staples on those ends to hold it in place if necessary. Then do the middle! The middle really has to be tight first before you can work back to the ends. You don't want to end up with loose material in the middle of the seat.
Here are some shots of all my stapling.

Here are my shots of the finished seat. This is just about as thin as this seat can be. Note how nicely the bevel came out and how nice and smooth the cover is. I'm really happy with it.

Another sample
These are shots of my Husky that I did about a year ago.
On this seat I removed much less foam. You can also se that I left this seat a bit rougher before covering it. The front foam was very thin and I was just hesitant to file too much away. The ridges in the foam ended up being invisible through the cover, but you could just feel them with your hand if you checked. So Ideally you would sand it a bit smoother than this. But you can how nicely even this thin cut came out!


  1. That's an excellent job on both bikes.


  2. Great tutorial, thanks! I'll be doing this over the winter for sure.

    I didn't see anywhere that you said how much lower the seat height is. From the chunk of off-cut foam it looks to be 2-3 inches thick. Did you measure the height before and after?


  3. Great tutorial, thanks!

    I didn't see it anywhere in there, but how much lower is your seat? The off-cut foam looks to be 2-3" thick. Do you have before and after measurements?

  4. Sorry for the double message. Google did some verification thing and I didn't realize it actually posted.

    With it so thin do you find it still offers enough support? I'm thinking I might only take mine down half as far as you did and test it out.

  5. Dave, the posts are delayed as I approve them individually to prevent spam. Actually, the problem with a deep cut is the V shape of the seat. It makes it hard to slide up your butt forward and back. For me, riding in the desert, almost all of my riding is standing, so it's not as big a deal, and it really helps when I have to put my foot down. I also have another seat, that I find myself using more often (especially for longer rides), that isn't cut as radically. and is much flatter. It is a low seat from "Seat Concepts":!/KTM-SX-SXF-EXC-XCW-*LOW*-2011SX-2013-2012-13-EXC-XC/p/13799880/category=1671352
    It is significantly lower than stock but also widens at the back for some seating comfort on long rides.
    That said, I really recommend cutting your seat. You can definitely start with less, just make a bunch of lines on your seat so you can easily cut more if you want. Remember, you can always climb on the bike and see what you think.
    Also, seat foam, or a whole seat, is not super expensive, so if it ends up badly, you can always buy another. ;-)

  6. Oh, to directly answer you question about the support of the remaining seat: It's hard but I don't feel the seat base through it. But the KTM seat has never been a "comfortable" one.
    I carefully examined the base before cutting and also really kind of probed how deep the foam is with my finders. I think I have an inch of foam above the base... ;-)

  7. Yes, I was thinking of probing through the foam to measure the depth before I start doing anything. That's a good point about not being able to slide back in the seat as easily. I was afraid of that. I spend most of my time standing on my bike too, but do sit down a fair bit in really tight technical stuff. Thanks for all the input. Great blog!

  8. Thanks for the compliment! Best wishes.

  9. Hi, I know this is an older blog but hoping you'll see it. I just bought a 2013 TE310 and I'm going to shave the seat down as much as possible. Do you have any inkling how many inches I could lose off that seat?

    I almost exclusively ride trail so I'm standing 80% of the time and never for long stretches.

    1. Take off as little as possible. Just enough to get one toe firmly down. If you take off too much, the seat becomes very valley shaped, and it becomes hard to move around on it when you need to.