making a tailpiece / bump stop seat for GS400

[perattzi]

If your top layer is still tacky, I have a little bottle of wax additive for polyester resin from when I made a seat for my old FZR600. I can send it to you for the 5 bucks or whatever in shipping.  I'll never use it...I'm going the epoxy route this time.

[Andy]

It hardened up, thanks for the offer though.

UPDATE
I scrapped the original attempt, I buggered it up.  Working on a second of differing shape.  Thinking about a third.
Picked up a 3.75 inch round LED stop/tail light from Princess Auto for $40.  A little more than I wanted to spend but it is the right size and BRIGHT and SNAPS on like lightning when you hit the brake.

[HerrDeacon]

Picked up a 3.75 inch round LED stop/tail light from Princess Auto for $40.  A little more than I wanted to spend but it is the right size and BRIGHT and SNAPS on like lightning when you hit the brake.

That sounds like the one I have. I got it on sale for $19 two years ago. I really like it. Extremely bright, I blinded myself when I was testing it out 

Be sure to post pics of the new tail as you progress.

[Andy]

Well I have made some progress on this front, I am on attempt #3 and I think I have the mold-making figured out anyway.

This one uses a plywood pan set into a recess in 2 inch foam.  The recess is there so that the seat will hide the frame tubes.  This is what I was going for when I ruined the original.  I actually used templates too, drew it up on the puter based on measurements off the original, printed them out and taped them on the foam for cutting.  Worked great!

To make the recess I made a very complicated, sophisticated, and expensive tool.  I traced the outline of the ply pan on the base layer of 2" foam leaving a 1 cm margin all the way around to make the sides.  Then I put the pan on the bike, and the tool (picture 2) on the pan.  Then I snapped the blade off so it only reached as far down as the bottom of the frame tube.  Then I heated the blade with a torch and used it to cut the line I traced for the edge of the pan.  Like a hot knife through carcinogenic butter.  then I made all kinds of criss-cross cuts.  The point of these was to be a depth guide for when I was carving out the recess -- when the lines started to disappear I stopped sanding and carving.  this gave me a pretty true base.  I dropped the ply back in and test fit (photo 3)

[Andy]

So at this point I had my solid base of ply sitting in a foam block that was cut to the exact, symmetrical (within reason) shape I wanted the bottom of the seat to be.  This is what I should have done the first time!  Then again, I never let not having a plan get in the way of attacking something.

Next  I just cut another 2" thick foam sheet to the same dimensions as the bottom one.  I tried to borrow my neighbor's jigsaw to make this step fast and square but he balked at 9 pm.  who can wait for tomorrow?  I used a hand saw and squared things off with my mouse sander, glued it on (photo 1)
then I drew up a few contours in Coreldraw and printed them off, and cut them out of the same foam.  I stacked them up and something was oddly familiar about the shape.  Aha!  I'm making a model of an offshore tug! (photos 2+3)

[Andy]

As much as I admire ships, I didn't want this bike to look like the piece of ship above.

A little shaving was in order (photo1)

Then a little more (Photo 2)

Then just a little fiddling to get a kick-up at the bottom rear and make more of a bullet shape (photo3)

Try to ignore the dummy in #3 he keeps popping in and screwing things up from time to time

[Andy]

I'm not entirely happy with the shape yet though.. I think it's too curved on top, I want to flatten it out a bit so it's closer to the original attempt, which I think complimented the shape of the tank.  I would love to get a long tank like on the old racers but hey, this is a $300 bike without a title so I'm sticking to the cheap stuff for now.  At least until I get papers for it, maybe then I'll go all out on a vintage look.

[Andy]

If/when I get hold of a 650 for a cafe project I'd be waaaayyyyy too lazy to go through all of that to have a bum-stop seat. .....Plus I really don't have a creative/artistic bone in my body.
I'll just spend the bux at Airtech and buy something off the shelf that will do the job.

I have never been able to get myself to pay someone good money to do something I could do half as well for a 10th of the price
I just gutted and redid the only bath in my house.  I had to pay a plumber to come hook up my tub drains... $380 bucks for 2 hours!  Other than stucco work around a window it was the only pro I had to call in.   Then end result isn't professional grade but neither was the cost, I figure I spent about 25-30% of what I would have on bringing in contractors.

[anarki650]

That's coming along damn nice!!! I used several different sizes of woodchucks (chisels with cheese grater like bodies, one side flat and one side rounded) an awful lot when I was working on my thesis sculpture work (same foam laminated with pigmented epoxy resin) a few years back.  Worked like a charm for me.  Takes the foam down quicker than low grit sand paper but without ripping chunks out of it.  Makes a hell of a mess though!!!

[Andy]

Hey Anarki, thanks for the kind words.  I am actually using a drywall rasp leftover from the reno mentioned above, it sounds pretty much like what you are describing - a 4 inche long and 1 inch wide cheese grater.

Then I smooth with the mouse sander.

The real discovery was smoothing out all the little ridges with a full sheet of 400 grit.  Hard to describe, but I held an end of the paper in each hand and "buffed" without letting my hands touch the mold.  the paper distributes the pressure way more evenly then blocks or hands and it really puts a nice smooth finish on there.
Damn I'm giving away my secrets, i have deluded myself into thinking I should make these part time and ebay them.  Custom fitted, you send me dimensions of your frame etc and an idea of the shape, I make it custom.  That's gotta be worth more than a mass produced item.  Of course, that implies great quality and that has yet to be seen!

[antiq]

I like it! In the pictures it does conform some to the tank though at the front instead of rear. Instead of foam on my build I'm planning to attempt fab with sheet metal. Just more into my comfort zone and perhaps a bit less messy.
The larger contour on your tail in the pictures gives plenty of space to build in a tail light.

[Andy]

More progress.
Made a thicker plywood pan.  Pretty much had to, the last stuff was just a little too weak.
I also figured out the mounting with a few suggestions from the BCCMCC guys (bc classic bike board).  One of them is an upholsterer and he suggested industrial strength velco he has, which he has been using for years with no issues on projects just like this.  I was a little worried about just velcro (this bike is for my fiancee, so I'm making sure it's SECURED to the frame) so I bought some 1 inch oak quarter round and glued and screwed it to the plywood pan so that the 1/4 round slots in between the frame rails.  It snaps into place and is TIGHT, preventing movement laterally and longitudinally.  Once the Velcro is on there I think it will take a solid tug to get the seat off the frame.

The hacked out recess on the bottom-front is to clear the airbox.

[supermandaddy]

I was curious how much builders are spending on bumpstops and other seats......I am all for diy to save some money but am starting to think that buying a rear bubble from roc city or other makers may be a little bit more convenient and cost effective, and then do the upholstery diy......any thoughts on this or prices that most are paying??

[Andy]

I am into this seat for a grand total of $50 CDN, including fiberglass cloth, matt, and resin.  That's about $46 USD right now.  That includes about $20 I wasted by being impatient.  My first one cost me about $18.

I checked out roc city myself and at a minimum of $105 plus shipping for the absolute cheapest thing they had (and I don't even like the thing) that still needs paint and upholstery, I think I'm doing ok.  I'm having fun too.

The unit I am making is completely customized to fit my bike and doesn't need any jury-rigging for mounting.

I can say I built this bike up myself (ok, not from scratch but more than many) and didn't just buy a bunch of stuff and bolt it on like Orange county choppers would.
As for convenience, hell yeah buying one is easier but for me it's not about easy.  It's not just about saving money either although if I had unlimited cash I doubt I'd be shaping foam for a 30 year old GS400 twin with no title in my 12x24 tin shed.

I'm sure guys like Anarki and HerrDeacon are just that much more happy with their bikes because they did it themselves.  check their bikes out, they are great and were done at home.  Deacon's graced the frontpage of dotheton.com for a couple months and Anarki's is one of the nicer cafe'd 650's I've seen, and I have trolled the net for hours looking for them.
Hard to argue with that kind of DIY.

[supermandaddy]

I have really been on the ropes for about 3 weeks now as to which way to go DIY or bought.....weighing the pros and cons of both sides....the one thing that I keep coming back to is the pride factor in the diy side.  Nothing beats starting and finishing a project saying I did that myself.  I appreciate the info and have a new motivation for getting in the garage more and off the couch.