Seat Rebuilding Project

[Easy-X]

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

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 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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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[stinkwheel]

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.

[Easy-X]

[stinkwheel]

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.

[struan80]

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.

[Easy-X]

Materials have started appearing

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
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[UncleFester]

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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2017 Z1000SX

[Easy-X]

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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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Easy-X]

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

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

<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

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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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Easy-X]

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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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Easy-X]

Finally! The sun is out so a good excuse to be out working

I glued the base layer onto the foam. Laminating helps the foam hold the curve I've been encouraging with the elastic bands. As it is all this foam comes on a roll anyway so it was half way there.

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

Went at the foam with a sanding disk, turned out well I think:

https://i.imgur.com/6qIYlKM.jpeg

A 40 or 60 disk is fine for this sort of foam and I found using a certain side of the disk and one direction of travel gave the best results in terms of reducing tearing and kicking. e.g. drill clockwise, right side of the disk, travelling leftwards. Practicing on offcuts of foam helps ofc.

The other tool I used was a Scotch-Brite mop wheel to do a bit of carving at the back end. Hard to see in the previous photo but I managed to reproduce the rear kickup. Easier to appreciate after gluing the thin layer of reflex foam:

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

If I have time tomorrow it'll be firing up the air compressor and stapling on the cover.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Easy-X]

Staple gun time. If you're in any way interested in upholstery buy a pneumatic staple gun, makes life so much easier! Obviously you need an air compressor but only 60~100psi (4~7bar.) End result...

https://i.imgur.com/t3mbkNd.jpeg

Not perfect but 90% there. Might settle down a bit after a few rides (as the actress said to the bishop!) TBH it doesn't feel that different - thanks to the layer of reflex foam - but I know the core is a brick compared to the old marshmallow. I think the transition to the pillion seat turned out well

A nice little adventure but what did it cost?

Foam

https://www.efoam.co.uk/

They'll cut any size and thickness you like. I bought 3 types of foam plus a can of glue £37 including postage. I reused the original cover but you might also factor in replacement vinyl.

Hot wire cutter

https://www.amazon.co.uk/dp/B09CH4D2DK

Amazon £35, but you could substitute an old electric carving knife, maybe a really, really sharp knife at a pinch.

Air stapler

https://www.powertoolsdirect.com/clarke-csg1c-22-gauge-air-stapler

£33 + postage. IMO an essential item, a hand stapler wouldn't work on this seat base at all. (Plus a box of staples, £8)

I also used a drill + sanding disks but I'll not count those as "extra tools." Might want one of these to carve into things:

https://www.amazon.co.uk/dp/B002QRWHT2

All together probably a comparable price to sending it away for a basic rebuild (but not cost effective if you count the time.)
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[WD Forte]

Not bad at all
could have done with some tassels and a few skull or live to ride
badges for the proper real biker look.
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bikers smell of wee

[A100man]

[Easy-X]

I wasn't after a "diamond stitched look at me" seat. Bone stock aesthetic with proper support, thank you very much I think the thin layer of reflex foam I used goes some way to prove you only need a little for initial comfort not the entire seat made of marshmallow.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[WD Forte]

needs a butt plug
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bikers smell of wee

[Easy-X]

A comment after sitting on it for a while* first 5 mins make me wonder if I hadn't overdone the seat foam firmness. However, it gets better over time (>20mins) whereas the old seat foam was the exact opposite.

I went for the 9lb reconstituted foam but I'd probably recommend the 6lb stuff if you're keeping your journeys under an hour.

*which wouldn't have sounded too bad if not for the preceding post!
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter