CB750F Project: Part IV

Not much progress, but I've been busy nonetheless.

I had the rear chocks off, trying to see if/how to take them apart for painting/powdercoating, but since these are the gas-charged units, I don't see a way to take them apart. My Clymer's book says there is a locknut under the top eye, but I don't see it, even though I compressed the springs. Well, it may be time to bring the shocks to someone who knows what they are doing.

I spent the past couple of days grinding, filling, sanding, and priming. The tank became the first victim to my fury. Armed with a sander, I removed all of the factory paint to bare metal. And a good decision this was, as the tank had surface rust under the factory primer. Once I smoothed my fiberglass filler and topcoated it with glazing putty, it was time for a thin coat of etching primer. So far so good. Things, however, did not work out that well, since I screwed up. What did I do wrong? Well, prior to priming, I wiped the tank down with some paint thinner (yeah, a bad choice, but that's what I had on hand). At first all appeared fine, but when I topcoated the etching primer with a sandable primer, one repaired area showed signs on trouble. The largest repair patch on the tank soaked up the paint thinner and, despite the hot sunny day, did not dry well enough. To make this short, the sandable primer bubbled up by day 2, and never hardened. I ground the filler out tonight, cleaned the metal, feathered the surrounding area, and applied some new filler. Now it's a waiting game. The rest of the tank is almost done, wet-sanded with a 320 grit, and ready for the last primer coat, which will come once all is smooth and the damaged area repaired.

There is some progress with the rear fender/cowl. As of today, the plug has been glassed (4 layers of cloth), and is ready for trimming. Once I pull it off the plug, I plan to do an extra layer (or two) of mat + resin from the inside, to provide additional strength.

Of course, the dreaded part still awaits me: Sanding the glass and prepping it for paint, which will take some time to do. 

Seat plug

After many, many hours of sawing, rasping, and sanding, I'm finally starting to see the light at the end of the tunnel. Well, not yet, as the most difficult part has yet to be undertaken. I'm speaking of glassing the plug, of course.

Nevertheless, I'm somewhat relieved that the plug portion is in its final stages. I'm currently waiting for the latex paint I applied earlier to dry, and once that is ready, I'll be doing the final sanding.

Why latex? Firstly, it the glossy paint will show any surface imperfections much easier than the dull surface of the sanded foam. And secondly, the paint will provide some level of protection against any accidental splatter of whatever chemical crap I find myself working with. (I learned today that both Bondo filler, and a high build primer, are more than happy to dissolve this foam).

So, without further ado, here is the plug, one step away from being completed.

And a mock-up shot with a taillight.

Oh, the dreaded seat

Well, I'm tossing the cafe-style seat concept out the door. Money and time spent, lesson learned, and life goes on. I am, however, not giving up. Yup, I'm a stubborn son of a ...

The F model simply does not lend itself to become a cafe bike. It has its own sexy lines, and I'd like to preserve those lines as best as I can, minus the tail section. Yes, I know the purists will hate me, but this is my bike, and I hate the stock tail. So, to the best of my abilities, I'll be trying to make a new plug, and play with a different style tail.

Lessons learned? Plenty: take my time; use rigid foam and not the crappy expanding stuff in a can; draw before you cut (hmm, sounds obvious, doesn't it?); fiberglass is a learning process; a better, more expensive resin does not stink as bad as the cheap stuff; mat is stronger than cloth; and time (again) -- don't try to rush it.

Thus armed with my newly acquired knowledge, I bought some pink rigid foam at Home Depot, got some 3M glue, and got going again. This time, I started with a solid block of glued-up foam layers. I went below the frame rails, as I want those to be hidden, for a nice, clean look.

Here is the current concept for the tail section. Don;t laugh at my drawing in-abilities.

And here is the clean, blank block of foam.

From the rear (decreasing width like the gas tank).

And after I cut the lower portion to follow the stock lines of the side covers.

In the end, this may not work out. I'm having fun with some foam and a rasp nevertheless.

CB750F Project: Part III

After two failed attempts with fiberglass, I was finally able to make a solid shell today. My previous attempts were doomed partly because of my inexperience (first time working with fiberglass), and partly because I was dealing with a not-so-good resin. So, still discouraged despite the many wasted hours, I trashed the bastard creations along with the bad resin, and went to a local parts store to get something better. This time, things actually worked better.
I ended up using fiberglass mat instead of cloth for the base. While this is considerably stronger than the cloth, I quickly discovered that working the resin into the mat can be pretty tricky. The loose strands like to stick to the brush, and eventually end up clumping in the resin. I'm sure by now some experienced fiberglass guru is laughing his ass off at me, but hey, at least I try. Anyway, three layers of mat followed by a single layer of cloth for a smoother finish, I ended up with a usable shell. I can't even begin to count how many hours and how much money it cost me.

Now comes the part where I have to make a decision. My initial idea was to leave the tailsection open, looking something like this (not the end product - trimming, sanding still needed)

But then I played around with the idea of incorporating the stock fender into the design.

And then I thought of yet another setup.

Well, at this points it is still up in the air, although I'm leaning towards incorporating the stock rear fender.

On a positive note: Yesterday I received my new handlebars. After much consideration I went with "superbike" bars, as they allow for more comfort and actually clear the tank at a full turn. So far, without the seat foam in place, the riding position feels rather comfortable.

CB750F Project: part II

I spent the past two evenings attempting to sculpt the new tail section on the bike. When it comes to designing, I'm more of a visual person, so I need to see things in place. Forget about using Photoshop! So, armed with several cans of expanding foam insulation, a discarded kitchen knife, a rasp, and some sand paper, I went to work. Needless to say, things never go as they should, but here is an update nonetheless.

Tail number one. This first attempt started life as a block of cured foam

After much hacking, rasping, and sanding, I got to a point where I sort of liked it, and decides to try my hand at fiberglass. Hmm...never done that before, although I used plenty of body fillers with success. How hard could it be? Well, it's pretty weird. I spread the cloth, stapled it to the foam, mixed my resin, and started spreading it with an old paint brush. The resin flows like molasses and sticks worse than honey. Within minutes I was in trouble and so was my foam. I ripped the mat off, but it was too late. Unfortunately, I don't have any pictures of the mold before it got eaten away by the resin, but here is one just before it got real nasty. You can still get an idea of what shape I was going for.

After I ripped the foam off and cleaned all the sticky mess, I started building up a new block for attempt number 2.

While the foam was curing (overnight), I thought about the tailsection. The more I thought the less I liked the cafe style tail on this bike. Don't get me wrong, I like the simple, round tails, but something about this bike makes it not flow. Maybe it is the seat I'm trying to make, maybe it is the long chassis. Either way, with attempt number two, I decided to try something that will flow with the bike's lines better. Just remember: this is very subjective opinion.
So, tail number two looks nothing like a cafe.

This is likely not the final shape, but here is a semi-frontal view:

And the rear view, with mocked up taillight I had laying around. I even think that the round light will go well with the bike.

Of course, the stock fender is only there to support the foam and to get the inside lines right. It will be eliminated as I progress. And yes, I know the light is off-center in this pic.

CB750F Project: part I

I found her sitting in the front lawn of a house next town over. Neglected by her previous master, the old man who put her in front of his house took her home two weeks earlier. Maybe things between them did not work out as he had imagined they would...maybe it was a matter of personality. I'll never know. Either way, he thought she was too much for him. I knew there and then that I had to save her.
 
Friday, after lunch, I brought her home. Dust covered, she sat on the trailer, strapped down in a way no self-respecting old lady would ever want to be seen in public. Still, she did not complain.

As I walked around her running my fingers along her once smooth lines, I felt the wrinkles age engraves in everything in this world. She stunk of old rubber and bad gas, but her allure was still there...just under the surface, begging to be discovered. Yet, bastardly as it was of me, I left her there waiting for me until the evening.

Little did I know I was going to pay for my selfish attitude. Perhaps she got jealous of the younger ones she saw in the garage,  or perhaps she just didn't care for me leaving her there all day. Either way, she gave me a nasty gash when I was trying to bring her down from the trailer. I sat on top of her and untied the first strap. Suddenly, she bucked to the side and threw me off. I had just enough time to jump to the side before she could land on me. Seeing this, she fells faster and landed on my ankle, pinning me down against the trailer. Full of adrenaline, I wiggled my foot free, grabbed her, and stood her upright. She hasn't tried to do that since.

So, let me introduce you to her, a 1980 CB750F Super Sport.

The motor ran, but only on three cylinders. My initial thought was to save this project for the long winter ahead, but the mysterious running issue kept bothering me. I knew I had to dive in and work on it.

I checked spark, fuel, and all seemed to be there. So I took the carbs and the airbox out, and proceeded to clean the carburetors.

It turns out that someone installed one float upside down. Still, while at it, I cleaned all jets and passages, tightened all screw, and soaked gaskets in brake fluid. Then I put it all back together (except the airbox which had the wrong filter element inside).
Upon starting, all four cylinders came alive. I'll have to wait for a full adjustment until I get a new air filter, but for now the faulty cylinder issue has been solved.

There are a couple of things on this bike that are just plain wrong. namely the seat and the handlebars, but there are many more issues I'll need to work on.

I took the seat off, stripped the upholstery and foam, and discovered that I don't like the shape of the pan. Since this bike is not exactly a cafe-racer (although it can be made that way), I decided against the traditional cafe seat in place of a comfortable, low seat. My initial thought was to make my own pan (here is another first one), but after seeing the lines, bends, and curves in the fender and seat area, I decided to try something else. Since my KLR250 Project, I've had a spare KLR seat sitting on the shelf. I took the foam off and tried fitting it. Yup, with a little modification it could be made to work. I like the way the KLR seat comes up against the tank, and follows through. The pan has to be bend a little, curved a little, and cut a little, but it should work. For the fitting, I bolted the pan thought to the battery box up front, and the fender bracket in the rear.

There is a little shaping involved to follow the lines of the battery covers.

And I still have to figure out what to do with the rear section. I'm thinking fiberglass, and a lots of shaping.

For now though, I'm excited even about the possibility of having a custom-made seat from an old KLR seat. Who would have thought.

This project may take some time. After all, the summer is here and I have two bikes that need to get out every now and then. But I'll keep you posted.

It's been a while since I posted anything, so here is a quick rundown:
I went on a nice group ride exploring local trails. It was a lot of fun until the end, when my front tire caught on a log submerged in mud, and I had to drop the bike in order to prevent a head-on collision with a tree. Thanks to my boots, I ended up being okay, and the bike only lost its left footpeg. No harm done, as I had a spare one at home. Unfortunately, I had to cut the ride short.

Since then I've been rather busy working on the house, but I'll spare you, and won't get into that.

While working on the house though, a friend stopped by on his recently-acquired motorcycle, and while I don't recall what make or model it was, it stirred something up inside me...something dormant for quite some time: I really want to make a cafe bike project.
You see, his bike was old (well, maybe 30 years), simple, and awesome. It wasn't restored, it wasn't chopped, the chrome was half-gone, and the paint was flaking. but the lines just worked together, the engine looked beautiful, and the sound was plain raw, like the sound I remember from my teenage years. I tried building an old school bike a few years back, but it wasn't the same.

So, now that the forgotten desires resurfaced once again, I hope you'll join me on the next project: 1980 CB750F.