78 CB400 Hawk cafe style seat

[williamsr815]

Well my winter project this year is to tear into my CB400TII and the biggest hurdle so far is creating a seat that i like. I am going to go with the cafe style because i have no need for a passenger and i really like the shape of the tank i found. I have been working on the seat for about a month now with some progress. I started a build thread over on caferacers.net, you can check it out here: http://caferacer.net/forum.html

To start out, I went to the local junkyard and found a stock seat so i could use the pan and the foam. At the time i had also found a suzuki gas tank that i was thinking about using to make the hump behind the seat.
Here isthe progress i made with that combination:

After i realized the tank was way too small, i ditched it and repaired what i had done to the seat pan.
I went back to the junkyard and found an old Yamaha gas tank that fit the shape of the bike much better.

From there i stripped everything and mocked it up on the bike to figure out where i wanted to cut it.

I want to keep the line of the gas tank flowing into the seat so thats where i mocked up the tank.
Once i got the Line marked i cut it and then removed the bottom so it would fit around the seat pan.

My plan now is to create a compartment in the tank so i can store small things while i ride. I wanted to make a flat bottom for the compartment and then fabricate a door for access. I made a template out of cardboard and then cut it out of sheet metal.

Before I cut the tank i had to fill in the area where the dip was for the gas filler. I took some fiberglass resin and let it set.

I made a homemade sheet metal brake and bent the pan:

This is where i am not but its covered in primer. I intend on taking seam sealer and filling in all of the gaps where the tank and the pan meet. I want to try and make the compartment watertight.

My next thing I need to do is fill all of the seams, weld the pan in place and then finish fabricating the door. Then i will start body work. For the seat i am trying to model it after this:

I want to make the rear cushion seperate and give access to the door in the hump.
My question now is, How do you attatch metal snaps to sheet metal? Can you use rivets or what?
Thanks for thehelp guys i will keep this updated as i make progress.

 

[williamsr815]

I Made some progress over the past few days.

I ran out of gas for my welder so i just tacked on what i could until i get more monday. I sprayed the inside of the tank with a rubberized paint to keep stuff from rattling around inside all the time. Once i get everything welded up im going to seal it and then start body work. Hopefully i will have it painted by the end of the week.

On another note my engine is getting finished right now, i should be getting it back sometime this week as well.

 

[d9canada]

You can get snaps that fasten on with screws, so drill a small pilot hole and use a self tapping screw with a drop of blue Loctite, hit the inside with a small grinder to grind off the sharp bits. Looks kinda big for the bike but you're doing a nice job of it!

Another option would have been to hinge the whole cowl piece from the back. You could have then put padding under the part currently covered by flat steel, so with the cowl up, you could take a passenger. Just my 2 cents, but don't quit, you're doing it for you!

 

[williamsr815]

Thanks for the info about the snaps, i will have to search for them. I have regular fabric snaps that i may be able to rivet on but i haven't quite gotten there. As for the size, i have gotten that from a few people and it might be a little larger than most but i have not been a fan of the softball sized humps some cafes have on them. Plus that was the size of the tank i ended up with so we will see how it goes. And since this will only be my second year of riding on the street, i don't want to even have the option of having a passenger quite yet. By the time I'm ready for one i will have upgraded to a new bike hopefully.
My next hurdle is going to be creating a seat cushion that hinges and allows me to have access to the door while looking good. I'm thinking about having the rear section of the cushion connected directly to the door so the magnetic latch holds the back in place. I'm also going to have to teach myself how to sew up a proper seat myself since i cant really afford an upholsterer.

 

[kwazykid]

I like where you are going with this. You might want to consider how thick you want to make the padding on the seat. If you go right up to the bottom of your door then the padding would binde and wouldn't open very well. If you had the padding on the back hinge upward then you could give your butt a little more padding and still be able to access the door. Just a thought... I'm sure what ever you come up with will work fine though. Keep it up!

 

[williamsr815]

I have been considering tapering the foam front to back in order to clear the hinge because if i level the foam as the hinge, there wont be enough cushion for my boney ass. Im probably going to do a very thin layer of padding on the back since in a normal riding position i wont even be making contact with it.

 

[williamsr815]

Well i made some progress this week over spring break. I finished 90% of the body work and rebuilt the caliper and forks. I went ahead and put the front end back together all i need to do is get a new brake line and bleed them. Hopefully thins week i will get paint on it and make some progress on the seat. I got some vinyl today that i think will work but we will see. Now on to the stuff everyone cars about!