'81 GS450L Cafe Project

[gjohnson]

I am starting a rebuild to turn an '81 GS450L into a cafe racer. There's one problem, I live in a condo without a garage. Luckily I have two spare bedrooms and one has a back porch at ground level.

The GS450L when I brought it home:

I threw a set of clubman handle bars on it to see the cafe racer profile.

The first step is converting my study to be used as a motorcycle workshop. I moved some furniture out and laid down some plastic to protect the floor from any spills, accidents, etc.

This is my first time ever rebuilding a motorcycle or doing any fiberglass work, so if you have some pointers as I go feel free to post!

The Build Start:
I wanted to start this build with trying to teach myself how to work with fiberglass (something I have never done.) I watched a lot of videos online about techniques and mold making before attempting this.

I went to Home Depot and picked up some R-10 foam board, carpenters wood glue, sand paper & sanding blocks, face masks to keep the dust out of my lungs, and a few other little things. All in all I spent about $40 at home depot for all of the supplies. I also picked up fiber glassing supplies after a lengthy talk with an employee at TAP Plastics, i ended up getting out of there with a small self-made fiber glassing kit for about $60.

It?s time to start cutting the foam to make a mold. I measured out the size I wanted my seat and rear tail to be and started cutting out a very rough shape.

Next I glued the tail section together and set a heavy can of resin mix on it to allow it to dry for 24 hours.

The glue setup nicely, so I started shaping it more trimming the edges a bit.
I started sanding by hand (I prefer to sand by hand so I can move slowly and carefully, it?s also kind of relaxing)

That?s as much progress as I have made so far.
As for the future, once I get it completely shaped I am going to bondo over the entire thing and sand it back down again (If the mold turns out nice I may use it multiple times and I want to protect it a bit.) I am hoping by the end of this weekend I will have my first fiberglass seat prototype. If you have any questions about the build, please ask.

 

[Flaming Chainsaws]

Cool! Another GS450L cafe project

You have a great start to the seat but the hump looks too tall and the flat spot on top isn't very pretty. Oh, and I think the it should be curved right behind the seating area instead of 90 degrees. Just my opinion.

For all your cafe needs, questions, and inspiration, go to DO THE TON!

http://www.dotheton.com/forum/index.php

I'll be watching this one!

 

[Ranger]

No exp. building a cafe racer but seeing as you have hardwood floors, if you haven't already it might benefit you to put plywood down with something soft and kind of think inbetween the floor and the wood to save dents in it.

Enjoy.

 

[gjohnson]

Flaming - absolutely, i am going to cut the back down a bit and try to get it nice and round all the way up to the back. Sanding by hand takes some time lol.

Ranger - I was planning on getting some of those weight lifting mats (the rubber ones made for dropping weights on them) just in case.

 

[Hoosier Daddy]

CONGRATS!
Posting to watch / help if I can. Google search images for "Bum Stop" as well as "Cafe Seat"... and +1 for DTT

 

[Ranger]

Flaming - absolutely, i am going to cut the back down a bit and try to get it nice and round all the way up to the back. Sanding by hand takes some time lol.

Ranger - I was planning on getting some of those weight lifting mats (the rubber ones made for dropping weights on them) just in case.

Good, but there is no "just in case" its always for "when it happens"
:-s

 

[spyug]

If you want to speed up the process there is no need to 'bondo" the plug, simply "wrap" it in plastic packing tape. Just make sure that the skin is impermeable since the resin will melt the foam if it gets to it.

If you want an even easier method, you can use epoxy resin and apply your glass cloth directly to the foam. This makes for an extremely rigid and light seat pan.

Before you actually construct the seat/tail, you should try the form on the bike as it may need some fine tuning. The first one I did I found to be too wide and high where my legs would go causing it to rub and pinch my thighs. Very uncomfortable. You will also want to think how you will attach it to the bike frame. You may need to fabricate brackets to be "glassed" into the seat pan too.

When forming the "hump" its most pleasing to look at when it follows the curve of the tank so again mock up the plug on the frame of the bike and view it from all the angles before you get too happy with the resin and cloth.

Fabing fiberglass parts is a lot of fun. Messy but fun

Enjoy and keep us informed of how it goes.

Cheers & good luck,
Spyug

 

[gjohnson]

I want to bondo it so it will last longer, if this bike turns out nice I might make a few for people if they are interested.

I finished up the foam board mold and it will be ready for bondo tomorrow night. and sanding Saturday... fiberglass on Sunday?

I wanted the seat to be a little shorter, I like the look of the rear tire sticking out past the bump a few inches.

Here's the pictures:

 

[Flaming Chainsaws]

Yum. That's looking better

 

[Guest]

Welcome to the forum and it's great to see another 450 coming along and getting some attention.

I like what you're doing so far and can't wait to see how it progresses.

 

[kparrott]

Thats seat looks good! Great job!

 

[gjohnson]

Thanks for the support everybody going to pickup some bondo on my way home from work today. Does anybody have a recommended brand?

 

[Runningdog]

+2 on DTT!!! Very creative bunch over there.

 

[spyug]

Well not to spoil your plan but bondo is not the right material to make a lasting "buck". Bondo will shrink, crack and or split. It may give a few months of use but once you get into hotter and humid weather its going to cause issues. To do it right you need fiberglass.

The method I mentioned works just as well or better as the tape can easily be replaced if anything happens to it. With multiple layers of tape it will last for a long time.

Just speaking from 20+ years of experience.

Good luck with it.

Spyug

 

[gjohnson]

So do you think I should wrap the foam in tape, then fiber glass over the top of that for the mold (so the wold would essentially be fiberglass,) then I could make my seat pan by putting fiber glass on fiber glass with gelcoat between?

 

[Tom R]

You wouldn't use gel coat in between layers. Gel coat is great if you have a female mold, which you don't. You could spray gel coat as a final coat; but why would you when paint is so much easier?
I'll +1 on epoxy being much easier to work with, albeit a bit more expensive; but for the small amount you need....
One of the problems with epoxy though is it doesn't wet fiberglass mat out as well as polyester - it might be harder to make some of your turns with it. So you might be better off using several layers of lightweight cloth ~ 4 oz or so.
Then long strokes when your sanding it smooth - an epoxy filler is handy here. I've made my own in the past by mixing micro balloons with epoxy with good results; though the pre-made goo is easiest to work with.

If you are planning on making more than one of these - you should make a female mold.

 

[Hoosier Daddy]

For my GL seat I used locktites 15 minute two part epoxy, mixxed it and then quickly thinned with rubbing alcohol to a "thin Paint" consistancy. Then painted it onto my foam and let it cure. After about 3 coats it totally sealed the foam buck. I then covered it with a sheet of tin foil for an extra measure.
I layed my 5 coats of glass cloth with standard styrene resin and once that cured was able to pop out my buck in one piece.
I even passed it onto a member on a different forum and He used to make his seat, so I know it held up.

 

[gjohnson]

Why would I not just use the male mold and go over the top of it to make multiple seats?

 

[Tom R]

Are you covering the whole thing with vinyl? I assumed the tail piece would be showing. If you are covering the whole thing then you're right, why not.
If you're making multiple seats it seems the finish work would be much faster if you only had to fair the mold once (female). Then you could use gel coat for a perfect finish every time. Again though, you only have to fair it if it's showing.

 

[Hoosier Daddy]

Yes, you don't have to.... but it's a PITA to get the glass smooth enough to paint without a female mold. Lots of sanding and any exposed glass would show big time. I used just the male buck but covered the entire seat with foam & vinyl.