Topic: '78 CB750K, refreshing and improving!

[rivetslag]

I hope it's ok that this isn't a full rebuild/resto project. I just bought this bike a few weeks ago, here is what it looked like at the seller's place:



I've been lurking these forums for a few weeks now, since coming upon this bike at the side of the road and needing to know more. I learned to ride on a friend's '79 GS550 when I was a teenager, but I haven't ridden since. Every spring since then I've gotten the itch to be out on two wheels. Finally this summer I couldn't bear it any longer, and I made the impulse purchase.

I had a decided dislike for the color, and I wanted to get to "know" my new bike by tearing it apart a bit. I decided to refresh my painting skills, to begin with. I'm a semi-professional painter as part of a trade I learned from my father, restoring pre-/post-War antique and classic mahogany runabouts. Basically, I fly by the seat of my pants, I don't actually know much about the chemistry behind the process. I wasn't sure if the combination of paints I dredged up from storage were going to work together, but I wanted to attempt a $0 paint job. I found a 2 part epoxy primer made by a now defunct company named Stoppani. This company went through a few names (Rivale was the other I recall), but I believe it began life supplying finish products for the amazing Italian boatbuilding company, Riva. (An interesting side story, those boats basically parallel the Italian's reputation in other arenas like Ferrari for cars, and Ducati for bikes)

So, anyways. I spent a few hours in the basement over the past few days. I sanded, and then smoothed out a few coats of body filler:



and then put on three coats of primer:



Yes, I brushed it on. I sanded it fair with another patch or two of body filler to smooth out the rust spots on the bottom edge, and the dent above the petcock.

Today, I headed out to our little storage garage (nicely equipped with a compressor and Snap-On box) to shoot some base/clear. From the beginning, I had wanted to go for a cobalt blue. I have always loved the blue colors Maxfield Parrish used consistently throughout his work. Apparently some even consider "cobalt blue" to be properly named "parrish blue". He achieved an intensity that has to be seen to be appreciated using an alternating process of laying down a watery blue, then a layer of varnish, then blue...etc. Yeah, I have neither the time nor the inclination to make this bike a work of art. That's something I'm saving for the day I do a frame-off on it, if that ever happens. I can't afford to get any paint mixed up anyways, petro-chemicals are so expensive right now. Let's just see what's kicking around...

So, rummaging through old rusty cans of paint, I was directed by my father to a can of base he had left from matching his old Super Duty's scheme. He'd never used it, and the truck is long gone. I did not like the dark blue of that truck, and was loathe to put it on my bike, but...$0 budget!

I set up a work table with sawhorses and an old door. I'm not kidding. Things have been a lot different since we sold the old business =\



I got to work spraying on a few coats of base: one tack, two wet, until I was satisfied. I disappointed myself with one sag, but if I don't tell you where it is....

Lo, where did this amazing color come from?



I had painted my gas cap last night, and noticed then that the color really didn't seem to match what was daubed on the can top. It also REALLY did not match my recollection of the old Super Duty. I got kinda amped, it does indeed look very cobalt blue, the very color I was daydreaming of (I even went to far as to fire up the GIMP and photochop up a tinted version of that first photo with a cobalt blue). It looks even better on the tank, with seven coats of clear on top. I'm probably going too far with the clear, but the massively layered and DEEP looking gloss effect is a taste I picked up from antique boats, with the depth of finish you can lose yourself in admiring the grain of tightly planked show boat's hull.

Speaking with my dad earlier this evening, he also is pretty confused on where that can of paint came from. All we can figure is that it was a fortunate mistint of that Super Duty's paint. I'm pretty happy with it. I'm going back out there tomorrow to do some water sanding on the clear because I messed up again, left a big drip on one side which I need to flatten and then reshoot.

I'm not sure if you guys like the step-by-step procedural walkthrough type project thread. Hopefully someone will get a kick out of this. The rest of the images are here: at my site's gallery.

Thanks for checking it out, and I'd love some feedback. I haven't decided what to do about the side covers yet. I've broken them twice already. Tomorrow I am going to lay up some fiberglass cloth to reinforce them from behind, and greatly increase the strength of the "bayonets" that clip onto the bike. Since I'm thinking I may have to carry a kit of 5-minute epoxy around with me everywhere for these things, I'm thinking maybe a simple one part gloss black may get applied to them. I'm thinking the black side covers might complement the nicely colored tank, make it pop a bit. Thoughts?

Some other stuff I'm going to do over the next few days: clutch cable, oil + filter change, new air filter, paint the exhaust black, remove engine guard, and a few other things. I'm also liking the idea of ammo box panniers, bar end mirrors, that cafe style oil pressure gauge, and fork gaiters. Maybe the tapered roller bearings for the steering head, too. At a point very soon now though, I'm just going to want to get riding, since it is on the road and all now. I also intend on taking a maiden voyage across the States to see the sights! My very long list of things to do is getting pared down every day =D

-hamilton

P.S. more to follow soon!

[MrHellpop]

Hey, that tank looks great! I am in the process of repainting the tank on my 77 also, so I am extremely interested in all the details, like how many coats of base, info on sanding, what kind of clear you used etc! Right now I am probably just going to do a rustoleum rattle can job on it, but I know it's going to turn out terrible. I do have access to a paint gun and compressor, but have never painted anything so I am a little intimidated. I don't expect to do a pro job, but I want it to at least look decent! Nice 77, btw... did you get a good deal on that badboy?

[rivetslag]

I put on three coats of base. The first was a tack coat, sprayed very lightly with low volume. I let that stand for about 3 minutes and then put on a wet coat. I ended up putting one more on because I had had to fiddle around with a paint chip and a bug, both of which had flown onto the top of the tank. I did get one sag with the base, but I wasn't patient enough to let it cure so I could wet sand it out. You can wet sand on base afaik, but especially with a drip, it's going to take awhile for it to cure hard enough to sand. I think I made the sag because I have no idea what the required gun pressure is for this base, for optimum atomization. I guessed. That did kinda discourage me, if I had been able to shoot inside (no exhaust fan, poor lighting), I could have left it at the second coat and had a perfect shot.

I used Matrix MS-42 clearcoat. I ended up stopping at seven coats of clear. This particular clear specifies a ten minute between-coat time, so total time for all of this was about two hours.

When you get to the clearcoating stage, it's a bit more forgiving. If you have a curtain/sag/drip, you can just keep firing through the rest of what's in your cup. The more you have on, the more you can wet sand without fear of blasting through to the base or stain. I didn't get around to it today, but tomorrow I will be finishing it up. I have some 1000 grit wet/dry I'm going to use, then hopefully shoot two or three more coats to finish it up. You know you're done when you've covered any visible scratches from the sanding process. When you're staring at it closely to check for that, you can also tell if your mixture is correct; that orange peel effect is most commonly due to incorrect atomization and/or an incorrect mixture of reducer. The finish should lie down like a sheet of glass.

I think you should skip the rusto-job and try shooting it yourself. If you have access to a gun and compressor, you should just shoot a few test panels first. Use a big piece of cardboard or, preferably, a section of sheet metal to get acclimated to the gun. Get used to adjusting your fan, fluid, and pressure, try to always keep the gun at the same distance and angle from the panel, and try it out. Less is more. Oh, and don't trust the person who used it before you, clean that sucker out first. Use gun solvent/lacquer thinner, and FULLY...FULLY disassemble it. Every part that can come apart comes apart. Use a bristle brush and scrub everything. Even a single metal flake stuck somewhere in there can give you a frowny face after you look back at your work. Keep a few ounces of lacquer thinner in the cup (and pull the trigger so it flows through the gun) if you're going to let the gun sit empty for any amount of time between mixing paints.

Umm...went off on a bit of a tangent there, didn't I. I wonder if this forum needs a full "painting" instructional.

I picked up the bike for $1000. I thought it was a good deal. I was just about to drive 4 hours to go pick up what was probably a basket case of a 1990 Suzuki GS500 when I drove by this one locally. It just seemed to make sense, so I changed up my plans. I'm pretty happy I did.

Oh, and one last thing. You might notice that in the first few shots, the tank is sitting on a bucket. That sucks, it's difficult to spin it around on demand when you're painting (which is kind of high pressure situation in which it is best to practice the philosophy of "slow is smooth, smooth is fast"). Another reason I think I made the one sag was because I started walking around the bench to keep moving around the tank, and it was dark on that side. Lighting is basically the most important factor in quality control, here. The difference that lazy susan made, which I found later, is not to be estimated. I would highly recommend you find something similar so you can stand stationary and just spin the tank around.

[poomwah]

nice shine on that paint job :]  and nice choice of color