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Seat Rebuilding Project

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Easy-X
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PostPosted: 20:22 - 20 Mar 2024    Post subject: Seat Rebuilding Project Reply with quote

As requested I shall journal my quest to rebuild a motorcycle seat...

Like so many bikes these days, the seat on my Husky leaves something to be desired after an hour or so of riding. The current Vitpilen factory seat is somewhat like the classic "long bench" with a slight nod to dirt bikes:

https://hqvadventure.com/forum/data/attachments/0/795-538de028c84233bb667f036b30f907e1.jpg

The similar Svartpiken seat comes in two parts:

https://hqvadventure.com/forum/data/attachments/0/794-2a81b4462eab13492a141c644ef75eca.jpg

I've got hold of the latter second-hand as I can skip re-upholstering the back/pillion part Smile

Comparison on the bike:

https://i.imgur.com/b9da4jU.jpeg

Both are covered by vinyl but the Vitpilen tries to fake a suede look:

https://i.imgur.com/XhS0YFH.jpeg

Let's take a look at how the seat is put together. Quick rifle through the tool drawer and one cup of tea later...

https://i.imgur.com/ZjaOBvr.jpeg

So classic vinyl cover over a single moulded piece of foam on a plastic tray base. Something worth noting if we look at the side views. Before:

https://i.imgur.com/hZnbtTx.jpeg

After:

https://i.imgur.com/WT7AOlT.jpeg

A bit of a kick-up to meet the pillion seat and a slight back-stop for your arse Smile First glance of a fancy foam shape might be a little intimidating - how could such a thing be replicated?

This foam is just a single piece of material; there are no layers of density or firmness. It's quite a bit thicker than I imagined due to the "tray" nature of the base. Even so, grabbing a handful proves the foam to be about the consistency of marshmallow. Thick and soft is great in the showroom and sufficient for a test ride but for several hours riding one would need something much firmer. Definitely scope for improvement.

The Plan

Looking at the seat tray, it lends itself to a simple layered structure. I'm thinking...

1) Fill the recess of the tray with very firm (bordering on rubber) foam to create a flat base.
2) Firm foam centre for most of the shape.
3) Memory foam covering out to the edges.
4) Try stapling a sheet of faux-Alcantara as a cover (with the original cover as a backup option.)
5) Optional: convert the pillion seat into something else. "Café Racer Cowl" is the obvious. Somewhere to stash drugs some tools would be nice.

The layers will be glued together but I don't think there's any need to glue to the base itself. The bottom layer (if cut snuggly enough) should lock everything in place. The top and bottom layers will be simple sheets whereas the middle layer will be two or three chunks glued together to get the front and back kick-ups.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter
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stinkwheel
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PostPosted: 20:27 - 20 Mar 2024    Post subject: Reply with quote

What about a gel pad in the void? You get big sheets of gel pad for wheelchair seats. Cut it to shape and tape the cut edge
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Easy-X
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PostPosted: 21:37 - 20 Mar 2024    Post subject: Reply with quote

stinkwheel wrote:
What about a gel pad in the void? You get big sheets of gel pad for wheelchair seats. Cut it to shape and tape the cut edge


I watched a video of some fancy boutique Harley seat maker in action. At each stage he'd throw an off-cut of vinyl over the work and let the customer sit on it, even go out on a test ride before the job was finished.

Good concept for a testing regime. If I hold off on gluing the layers together I can probably experiment with different materials see how things go. TBH though I mostly see people using a gel layer as a top insert but I might get some in as it's curious looking stuff Smile

In the meantime I've ordered some bits of reformed foam, closed cell foam and reflex (memory) foam along with something called "Scuba Suede" which is meant to be both stretchy and water resistant.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter
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stinkwheel
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PostPosted: 22:00 - 20 Mar 2024    Post subject: Reply with quote

That evostick spray adhesive is useful for sticking layers of foam/stuff together. It doesn't need to be very well held, just enough to stop it slipping apart while you stretch the cover over it, then that holds it all in place. It's what I use to glue high density foam kneeling pads into my canoes.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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struan80
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PostPosted: 22:02 - 20 Mar 2024    Post subject: Reply with quote

Memory foam topped with gel sounds comfortable. I've never sat on a bike yet that doesn't hurt my backside after a couple of hours. Strangely I find sportbike shaped bikes more comfortable. Good luck with the seat mate.
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Easy-X
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PostPosted: 00:29 - 23 Mar 2024    Post subject: Reply with quote

Materials have started appearing Smile

I can't be arsed to break out specific weights for a deflection test but if we say the factory foam is at least 30mm thick you can easily pinch it down to less than 10mm. "Reflex" foam layer pinches down to nothing, as one would expect. Closed cell squished down 50% and the reformed foam by about a third.

I have enough material with the three replacement layers to replicate the thickest part of the old seat foam but probably, given the centre core will be ~3x firmer, I could make something a bit thinner overall. The Husky has quite a tall seat height for such a small bike but mostly that's affected by the "John Wayne" leg spread than the peak height of the seat foam.

Regardless, here's a rough cut:

https://i.imgur.com/ju6WKZE.jpeg

Need to look in the toolbox for a long, sharp knife to start carving some shape. It might be possible to use a sanding disk but I have a feeling reformed foam will tear up. I've saved the offcuts for testing. I could probably throw the seat straight on the bike now just for testing...

https://i.imgur.com/OVYNAwT.jpeg

...maybe later Smile
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter
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UncleFester
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PostPosted: 07:28 - 23 Mar 2024    Post subject: Reply with quote

If you want to shape it, you can use a rotary polishing machine with a sanding disc on it. Creates a bit of dust but lets you shape things. Either that or a hot wire cutter.

I've used a sharp bread knife before pretty successfully too.

Got the gel packs from here - https://danmedicasouth.co.uk/product-category/motorcycle-seat-pads/

Also worth getting a layer of thin stretchy foam - it's foam with a material cloth backing. A layer of that stretched over the final piece and glued in place will help you get nice smooth edges and tie it all together before you put the final layer of vinyl over. Also helps the vinyl with being pulled / stretched into shape as it doesn't stick to the foam as you pull it around.

That's the stuff I used - https://www.gbfoamdirect.co.uk/product/scrim-foam-backed-car-headlining-material/?attribute_thickness=12mm+x+1000mm+x+1500mm
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Easy-X
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PostPosted: 12:33 - 23 Mar 2024    Post subject: Reply with quote

That's interesting. I'd bought some "Scuba Suede" thinking that I'd use it for the actual cover but I think I'll stick with the original vinyl. I could combine it with my reflex foam to make the top layer, as you suggest.

As for shaping it's: sharp knife, old-skewl electric carving knife, hot wire and sanding. I'll try all the tools and see how they compare so just waiting on a hot wire kit from Amazon.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter
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Easy-X
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PostPosted: 15:11 - 24 Mar 2024    Post subject: Reply with quote

Tool No.1 - Hot Wire

https://m.media-amazon.com/images/W/AVIF_800250-T2/images/I/71cYc3ixtVL._AC_SL640_.jpg

The above is a cheap kit from Amazon. I would suggest checking the specs for power output. Moar powa = easier to cut denser foam.

With care, the hot wire can make very straight precision cuts. Very little material is lost (the wire is ~0.2mm thick.) For the foam I'm using one would need to go at it very slowly but really the major limitation is the width of the wire. I can see if I want to cut out a curve I'd need to mark out the side profile and go a slice at a time, like cutting cheese Smile

I'm now eyeballing the rear hump of the seat again. It'd probably be more efficient to start with a thinner piece of foam for most of the seat and the rear bit as a separate glued on piece Thinking

<edit> Nope. Looking at the original foam the thickest part is actually the midpoint of the seat where it kicks up/forward so I'll still need to carve out the butt shape Smile

BTW the rods in the kit aren't much cop for cutting but they are good to resurface the foam that's torn up through rough cutting.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter
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Easy-X
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PostPosted: 04:22 - 28 Mar 2024    Post subject: Reply with quote

Totally misjudged the kick-up at the back so glued on some offcuts to build up the back. Just using the hot-wire I've got this far:

https://i.imgur.com/OKq3zgg.jpeg

Just throwing the cover over it the front actually looks a lot better than the photo. The centre's a bit too thick so I think the next step is to try the electric sander method. Hot wire's not much use for carving things out.

If (and bearing in mind it's the Easter weekend) the rain ever stops I should really throw it on the bike to try out.
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