Cafe seat fab for a Kawasaki H1A

Hi All,

I'm new to the forum but I've been working on this 'ol two stroke for the last couple of winters. Last winter I got serious about getting my solo seat off the drawing board and into production. I've owned the bike since the late '70's and way back in the day I picked up a tailpiece from a Z1. I seem to recall it as one of the first street bikes that had body parts other than the standard tank and side covers. Always liked the look of it and somehow, someday, I wanted to get it fitted to my H1, along with rearsets and clip-ons. I even had it painted way back when to match the rest of my bodywork.



Flash forward 25 or so years and here I am, still dicking around with it. I knew what I wanted but wasn't sure how I was gonna get there.
I'm not a machinist or fabricator but I'm fairly well equipped with hand and power tools. I did buy myself a Lincoln Electric MIG welder and can now make some really bad welds. I'm amazed at how useful a grinder can be...

First I thought I'd try and make a set of rails, then cut/bend/weld to fit a pan to cover the rails - mocking it all up with bits and pieces of metal and carboard from around my garage.





After a few frustrating attempts at this kind of thing the light bulb went on and I thought why not see about using an old stock seat pan and modify it - how hard could that be??
I just happened to have such a seat from a very rough H1 I'd recently hauled home.



Once I started tearing it apart I began to wonder if this was really the great idea I'd thought it was ...



Once I got it bead blasted it didn't look quite so bad (still really bad but without the rust!)
Top and bottom views:



First thing was to get it back into one piece. I mounted the two pieces onto a frame and welded them together (really badly) and went at the welds with a grinder till it didn't look half bad.





Next, it was both too wide and too long for the tailpiece to sit where I wanted it, so out came the grinder with a zip disc. From the previous picture you can see that I was limited to what I could take off by the brackets for rubbers bumpers, seat hinges and seat latch.



That got rid of a lot of the rot and I then made up new sides for it and welded them on.







More to come... Any feedback? Too many details? Too many pics? Let me know, guys. Don't want to wear out my welcome on my first visit.
I've taken hundreds of photos of my progress so I'm anxious to share some of them.

Cheers,
Neil

First of all, welcome to the forum! Its good to see you still cherish that old bike. The seats lookin good man! I don't think anybody is going to complain about too many pics/info. It's hard to learn TOO much.

looks sweet! Id love to learn to weld.

so are you still using the tail piece or are you ditching the idea?

H1? dont they get like 17 mpg?

Thanks, guys.

The tailpiece is still a go - I think it really compliments the lines of the '71 tank and side covers.

17 mpg?? I don't think they're that bad. They get at least 19 or 20.

More to come...

Cheers.

my june uk classic bikes mag had a write up on em and so did july motorcycle classics. thats where i got the 17 mpg from

theyre pretty sweet two strokes though.

Awesome work! Should be really bitchin. A guy I know has an H1 hes sending out somewhere to get restored to full factory specs. Amazing how much $$$ hes going to spend on this bike. And post a million pics if ya have em'. Cant wait to see this one finished!

I really want to buy a welder and tear into a project like you did. PROPS on having the cojones to at least give it a try. Who cares what the welds look like. As long as it makes you happy. I think your seat will turn out looking great.

Hi Guys, here`s my second installment:

The final touch for the pan was to trim one of the hinges so the seat would lift fully with tailpiece connected. I decided I'll use some light aircraft cable connecting the seat to the frame for a stop.



Next, it was time to fab some kind of taillight/license plate bracket to mount to the tailpiece. I wanted to use the stock taillight to maintain some of the the original look. It also tucks very nicely up under the end of the tailpiece so that it's not really visible from the sides. First I roughed it out with some cereal box cardboard, then made a cast with drywall mud to get the exact curvature of the underside of the tailpiece where it's going to fit.





Cut the piece from aluminum plate





Rubber gaskets cut from inner tubes between all pieces - cut the necessary holes to mount the taillight - and a test fit.







Bent the license plate portion of the bracket and made another of aluminum to support the back side. I have no idea whether this is all going to hold together on the road. I tried to overengineer it somewhat but time will tell...







Finally, a test fit of the whole assembly.



Still needing to be securely mounted to the plastic tailpiece. That`ll be the next installment...

Cheers,
Neil

nice planning and work!

It's looking great so far. So is it safe to assume there will be no rear fender?

noahdog said:

It's looking great so far. So is it safe to assume there will be no rear fender?

Click to expand...

Thanks. I'm using the plastic inner rear fender from a different Kaw triple. The underside of the tailpiece is trimmed to match the curvature of the top of the fender so the license plate bracket becomes a continuation of the fender (if that makes sense?).

Love it dude! Bring on the pics!!!
The quality of the work here is exceptional. This seat will look like it could have been manufactured by Kawasaki. I'm in lust with the taillight mount/tag bracket!

When its done this bike may be the closest thing to a real factory custom we have ever seen on here. Its really coming along great! Really terrific work. Reminds me of when car companies used to use parts from all their models and massage them a bit to build 1 show car back in the day...

Very nice work! It brings back memories of the 70's for me. I had two different H-1's. A 73 and a 74. I rode the 73 from near Portland, Oregon to Tijuana and back over a week's vacation. I was still young and foolish then. It got closer to 27 MPG as I recall. Gas was still an issue in some areas.

Keep up the great work!

Thanks for the kind words, guys.

I'm flattered - just another hack working in his garage...

What I'm trying to build is a period correct cafe bike with minimal modern upgrades. I've got shocks, rearsets, clip-ons and even a set of NOS expansion chambers from back in the day. My upgrade to a disc front end is simply a bolt-on from a '73 S2A 350cc triple. Come to think of it the only "modern" bits on it are the master cylinder, lever and caliper from a mid-90's Kaw EX500, similar vintage clutch lever, braided steel brake line, Sytech clutch release and cable, and tires, of course.

Once I get the seat thread done I'll be happy to start one that covers my project from the ground up.

Cheers,
Neil

Here I go again...the final episode in the seat saga

Had to design and make a few brackets to hold the taillight bracket to the tailpiece. Since the tailpiece is plastic I thought it best to sandwich it between aluminum plates using gaskets cut from inner tubes.









Next I started thinking about seat padding and mocked it up with some closed cell foam I had kicking around. I'm not completely sure what I'll finally use but it'll definately be held on with velcro.



Since the padding is much thinner than the stock seat I decided to carry it a little ways up the back of the tank. Had to cut a piece to weld onto the front of the pan to support this.





The final mocked up version when closed and open. As you can see, seatpan, tailpiece w/ taillight and licence plate will all be one piece. The front 'arms' of the tailpiece still need to be secured directly to the seat pan.



I like the way things worked out. Now it's time to take it all apart and finish up the pan. I used Bondo to fill all the rust holes. I only worried about the bottom side since the top will be covered.



Once the Bondo was sanded smooth I put a couple of coats of Duplicolor RustFix. Then came a few coats of gloss black Tremclad.



Followed up with some edge trim.



Powdercoated the taillight bracket



And , voila, this is how it currently sits. Still have to do some trimming on the plastic sides of the tailpiece, finalize the seat padding, add the support cable to hold the seat when it’s up, etc.

But most of the work on this seat is done. I'm currently working on finishing off the motor and hope to have it on the road in the spring.

Cheers,
Neil

Looking geat so far but are you going to cut the foam down at the front to match the pan? As it's pictured now it looks like the padding goes too high up the back of the tank. I think the front lip on your custom metal pan is about the right shape. I think covering the top of the seat with microcell foam and shaping it in place might do the trick. Are you going to wrap the padding down the sides of the seat to match the plastic tail piece lines?

noahdog said:

Looking geat so far but are you going to cut the foam down at the front to match the pan? As it's pictured now it looks like the padding goes too high up the back of the tank. I think the front lip on your custom metal pan is about the right shape. I think covering the top of the seat with microcell foam and shaping it in place might do the trick. Are you going to wrap the padding down the sides of the seat to match the plastic tail piece lines?

Click to expand...

Yes, the padding will be cut to match the front lip on the pan.

Not sure what microcell foam is, or where it can be obtained. I'd consider it if you can give me some details or a link.

I was just planning on a pad on the upper surface as the gloss black sides of the pan match the gloss black frame and the edges are nice and clean with the black edging. I have an upholsterer friend who said he'd make a leather cover for it but I'm not sure whether I want to go that route or just leave it with the bare foam look. Either way, I'm planning a removable pad secured with velcro.

Also, the liines of the tailpiece are going to change a bit - the long skinny 'arms' are going to be trimmed down so the top edges are parallel with the top edge of the seat pan. I'll try an post a pic later today that shows what I mean.

Cheers,
Neil

Microcell foam is a closed cell foam padding that is used for outdoor use and can be trimmed with a kitchen knife then shaped with a sanding pad. They use it alot in the marine industry for seat padding or the padded tops of knee wake boards and such. Here's a link to a site that sells it... http://www.foamandupholstery.com/minicell_foam.htm