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Author Topic: 1982 Yamaha XS400 Seca  (Read 22715 times)

Offline hdscarbro

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1982 Yamaha XS400 Seca
« on: Aug 07, 2014, 22:44:18 »
Found this sad 1982 Yamaha XS400 Seca on Cragislist for cheap. Bought it as a project to work on with my 14 year old son. I thought it would be fun to see if we could get it running again. The bike came from a guy who cleans out houses in exchange for the unwanted contents.

The original gas tank is missing. The tank in the photo doesnít fit, but was included in the deal. I think itís from a Suzuki. The carburetors are also missing.

This project is also documented (with more photos) in my XS400 blog.  We started this project a while back.  I'll do a couple more posts to bring things up to date soon.


Offline Weldangrind

  • Posts: 84
  • Quae nocent, docent
Re: 1982 Yamaha XS400 Seca
« Reply #1 on: Aug 08, 2014, 03:08:31 »
Interesting project.  I've considered that model for a few reasons, not the least of which is cheap insurance in my area.  That said, I'd prefer a twin shock bike.

The tank has potential.  The shape isn't bad, and the flip top cap is a bonus.  I see from your blog that you've found a different tank, and it looks like the stock type.

Nice job on the seat, as found in your blog.

Offline hdscarbro

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Re: 1982 Yamaha XS400 Seca
« Reply #2 on: Aug 08, 2014, 09:41:24 »
I found a stock tank on eBay a while back. I like the shape and it avoids the whole problem of fitting a different one.

Here's the bike with the beginnings of a seat. I'm using 2" insulating foam from my local building supply to fabricate the seat. It's glued using spray styrofoam adhesive from Michaels. Regular spray adhesive dissolves styrofoam.



The ultimate shape. I tried to carry some of the angles and shapes from the tank to the seat.



Replaced the styrofoam base of the seat with a rigid one made of wood and fiberboard. All of the shaping was done using a sanding block and 60 grit paper. As I a shaped the seat paper templates were used to help maintain symmetry.



Plug coated with tape and wax. The recess was created taping down split plastic wire loom that I  cut in half.  I tried using tubing on my first seat and it was a difficult to  tape in place.

I am using Butchers Wax to keep the epoxy from sticking.  It's available from woodworking suppliers . You can also get special mold wax, but I already had the Butchers Wax.



After several layers of fiberglass.  I've tried both mat and cloth in previous fiberglass projects. Mat is cheap and really messy to work with. I decided that I like 6oz cloth best.  It can be purchased from West Marine (a local store) or ordered from many suppliers. I like Jamestown Distributors. Ordered a gallon of epoxy and batch of fiberglass from them a while back.


Offline msjhydro

  • Posts: 2
Re: 1982 Yamaha XS400 Seca
« Reply #3 on: Aug 10, 2014, 01:30:14 »
I've thought about making one myself. But wasn't sure when I can buy one for $150 and be done! Lol

Offline Weldangrind

  • Posts: 84
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Re: 1982 Yamaha XS400 Seca
« Reply #4 on: Aug 11, 2014, 01:36:08 »
How did you make the bead along the bum stop and seat edge?  Do you plan to show us your Yamaha?

Offline hdscarbro

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Re: 1982 Yamaha XS400 Seca
« Reply #5 on: Aug 11, 2014, 09:49:36 »
I made the bead using split wire loom that was cut in half using a razor blade. Here's a photo of it. It's available at electronics supply stores if you don't want to order it.  There are perforations opposite the split that makes cutting it straight easy to do.

There are lots of photos of my SR250 on the blog I wrote after the build. I'm still adding details, but it's worth a look.

Offline Earlysport

  • Posts: 19
Re: 1982 Yamaha XS400 Seca
« Reply #6 on: Aug 13, 2014, 02:09:15 »
So you're the other guy building a twin cam XS400. I'm pretty sure that makes two of us in the world lol. I'm hoping I might be the first Seca to get a feature on BikeExif. Don't do anything too crazy and beat me to it OK :-)

Earlysport
XS400 DOHC build
http://www.dotheton.com/forum/index.php?topic=61363.0

Offline hdscarbro

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Re: 1982 Yamaha XS400 Seca
« Reply #7 on: Aug 13, 2014, 09:17:49 »
Maybe our DOHC XS400 builds are really ahead of the curve and by this time next year nearly every new build thread will be titled "Yet Another Twin Cam XS400"

I am happy to cede the BikeExif slot to you. I am not planning anything too crazy.

Offline hdscarbro

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Re: 1982 Yamaha XS400 Seca
« Reply #8 on: Aug 14, 2014, 12:37:11 »
Made another seat. The first one was too big and square. Also, I decided to have the seat sit over the back of the gas tank. The first wasn't wide enough at the front.

New seat being shaped.



After fiberglass layup.  I tried release fabric on this seat. I think it makes for a better initial finish. The epoxy is evened out better and there won't be nearly as much sanding.



Here's the seat on the bike.  Planning to use these "free" mufflers from a Yamaha Radian that I got from my cousin. They're currently loose fitted using  Emgo upswept muffler adapters.  WDYT?

The bits of paper on the floor are CAD (cardboard assisted design) scraps.



Selfie showing the tail light that I am planning to use.  I originally bought it for my SR250 project. I think it complements the shape of the seat pretty well.


« Last Edit: Aug 14, 2014, 12:51:41 by hdscarbro »

Offline Sav0r

  • Posts: 459
    • ChrisLivengood.net
Re: 1982 Yamaha XS400 Seca
« Reply #9 on: Aug 14, 2014, 15:30:00 »
That's some solid glass work you are doing there. Nothing like taking your time on the plug to get a good finish. I agree, cloth is the way to go. It's usually lighter, stronger, and easier to work. The only time I use mat is when i'm making molds. It's just cheaper. Generally speaking Aircraft Spruce has the best prices on cloth, its around $8 for bi and $9 for uni per yard.
Sav0r the adventure.

Visit www.chrislivengood.net to get more information on my RD350 dubbed Mia Wallace as well as my other projects and snafus.

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