78 GS 750 Rebuild

[nvr2old]

Solvent pop usually occurs when the clear, as you mentioned, is sprayed really thick and it gets a "crust" on the top before it has a chance to dry deeper down. The solvents don't have a chance to breathe and air out, get trapped..and "pop" More often then not, they're really deep and to get them completely out, you risk sanding into the base coat color, and then basically have to start over if you do. Sand them to the point you're comfortable with, and just re-clear over them. Start a bit dry and then build up to a few wetter coats to finish. They should fill up. It's also a good idea to keep air moving around your parts after your final clear coats with an oscillating fan..not on high to raise dirt in the air, but just enough to keep the air moving. It'll help dry from the inside out that way instead of getting a crust on top. It's all a learning experience and you're doing fine.

[Sam 78 GS750]

You can't really see it in the photos I posted before, because they weren't there yet. It looked great for a day before the solvent pop seemed to show up, but then the air bubbles gave the clear a really cloudy look.

You were right...they were really deep. When I would open up the ones I could see, there were still more trapped in the clear. Before I knew it, I had broken through to the base in spots so I figured I may as well sand all the clear off to get rid of all of the air bubbles. They went all the way down to the base.

Now I have all kinds of layers...clear still covering a lot of the tank, base in spots, various layers of primer, and I even broke through to metal in spots.

Not sure where to go from here. I'm between shooting a thin coat of primer to seal and then base and clear again...or just taking it all down, shooting one more round of high build just to make sure it's level after all that sanding, and then base and clear again.

What do you think?

20180927_083244 by samL9, on Flickr

[nvr2old]

Sorry for the delayed answer. Been on vacation this week. It's a shame you had to take your paint job so far back. Can you run your fingers over the sand throughs and feel the layers? If so, you'll have to go back to the high build primer to fill those areas again. If you can't feel the layers then I think I would spray a couple of VERY light coats of primer over the spots you've sanded through to. Especially where you hit bare metal. Keep them dry, too, If you spray them wet. it will lift, I guarantee. Let it set overnight, maybe take a bit of 600 to it to make sure it's smooth, re-base and re-clear. Again, when you re-start with your base coat, make sure you don't pour it on, because it will lift if you do because it's all so fresh still. Just enough base coat to cover and no more. Start the clear a bit dry to begin, and progressively get wetter towards your final coat, but as you've learned, not so wet that it runs, or you'll be starting over again.

Keep at it, nobody said this stuff is easy, even for someone whose done it for many years.

[Sam 78 GS750]

OK, so I could feel the layers so I hit it with primer and sanded again. Laying on the base for the 2nd time around, it wrinkled in one small area. It looked like what happened to Pete with his Kat in the silver. I did what he did...let it dry, sanded that spot back, resprayed, and kept it moving. So far, so good.

On to the clear. I didn't want to have to do this a third time, so I was pretty conservative on the coats. I did one dry coat, followed by one medium coat, and then a third medium wet coat. Then I let it be.

I'm thinking I need to do a couple more coats of clear to avoid sanding/buffing through into the color. There's some orange peel, and other spots that I think are from overspray, but I'm not sure. Since I layed it on super thin this time I want to make sure I have enough material to correct.

I scuffed it up with 800, since that's what the data sheet called for "if an additional application is desired after cure". Would I have any issues spraying a few more coats over the clear as it sits now, orange peel, overspray and all?

20181008_125209 by samL9, on Flickr

20181008_125224 by samL9, on Flickr

20181008_125233 by samL9, on Flickr


Not sure if this is overspray or not. I can only described it as "textured" or tiny orange peel...I don't know, it just looks dull and rough (it did even before I scuffed it with 800). I'm wondering if I clear over it again will it be fine, or will it look cloudy and I should sand it back more now
20181008_125303 by samL9, on Flickr

A bit closer...
20181008_125247 by samL9, on Flickr

[nvr2old]

That's just the texture you get when you spray it as dry as you have. I would sand it a bit more with 600. 800 isn't going to do much for you and really isn't enough tooth for the next coats to stick well. Only you know how much clear is on there, so don't push it to get it glass smooth if there's only one wet coat on there before you stopped. Yes, more clear to finish up with. At least three coats to have enough to sand and polish.

[Sam 78 GS750]

Ok, well that's reassuring. I picked up some more 600 grit, and will continue to sand with that.

I'm actually grateful for the orange peel, because I think I can use that as a guide for how much I can afford to sand.

For the spots near the front where I was concerned about the texture, I'm not sure how to tell how much clear I really have to work with. Those were spots where I had issues the first time around with it being way too wet, and I think I sped up my passes in those areas and overcompensated. That made it so even my somewhat wet coat ended up still being dry in those areas.

[Sam 78 GS750]

As a bit of a sanity check, I put water on the tank to get an idea of what it would look like with more clear over what's there. I could still see the texture and orange peel under the layer of water, but only if I looked really closely.

Is that a valid check/approximation?

[nvr2old]

Better to be safe then sorry at this point, Sam. As long as you have the entire surface scuffed up pretty well with the 600, just go with that and start the clear process again. The next round should fill in whatever orange peel is left.

[Sam 78 GS750]

I'm also worried about the body lines and down by the seams. That's where I always broke through first when sanding the primer... I want to make sure it's scuffed up enough so that the next coats stick, but not sand to the point where I break through. I think a very gentle touch is called for here.

Who knew painting could be such a heartbreaking enterprise? I feel like I'm so close right now. If I had to take it back down again, I think it would feel like my first breakup.

[nvr2old]

I know what you mean, Sam. I've been through exactly what you're going through. Just keep your sandpaper off the body lines or anywhere the clear might be thin after scuffing with the 600. As frustrating and scary as it is at this point, all will be replaced with a sense of satisfaction and accomplishment when you get your parts done. Be patient and focus and you'll be in great shape.

[Sam 78 GS750]

So I'm still at it. Got the tank scuffed up pretty good, and managed not to break through the clear in the process. Then I had a string of bad luck with the weather...super hot and close to 100% humidity every day for a stretch. Then all of a sudden it was too cold to paint. Finally hit a day 2 weeks ago where it was 68 and 50% humidity, so I got down to it.

I did get a couple of small runs, but nothing nearly as bad as last time. The solvent pop on the first round of clear didn't show up until a couple of days later, so this time I cut the runs down the next morning, and then lightly went over the entire tank with one of those 3M pads labeled "Ultra Fine: 800-1000 grit" just to open up the clear so it could breath.

Since then, I hit a couple of areas where the orange peel was kind of rough with 600, and then went over the entire tank with 1000>1500>2000 all using a soft block. Hard to tell for sure, but I think I got all the scratches from each previous grit with the next higher grit.

I masked off the seams and the area under the gas cap cover, and just stayed away from the body lines and corners... pretty much any area that broke through 1st when I was sanding the primer. Now I'm thinking of just going over the body lines lightly with the 2000 to just take the edge off the orange peel.

There are still some spots near edges that have orange peel and texture, but I'd rather live with those than burn through at this point. For the most part it's pretty flat though. I think that if I did sand enough at each grit to get the prior grit's scratches out, it should buff out very nicely!

These pics are all with the 1000 grit, I've taken it to 2000 since then...
20181110_150002 by samL9, on Flickr

The side I hadn't blocked yet, just lightly went over with the 3M pad.
20181110_150034 by samL9, on Flickr

not too bad off the bat, but a bit of orange peel. You can see the bike in the background of the reflection.
20181110_150105 by samL9, on Flickr

a bit closer.
20181110_150044 by samL9, on Flickr

I did get a couple of fisheyes this time around. They've diminished a bit more since I've sanded through to higher grits. Think they'll be noticeable after buffing out? I did google a bit, and some guys were showing that they mixed up a tiny batch of clear, and then filled them in with a drop of clear on a pin head. May just go that route and then sand a bit more with 2000 before buffing...
20181110_150128 by samL9, on Flickr

[Sam 78 GS750]

ok, so compound around the fisheyes took it from dull with shiny dimples to shiny with shiny dimples... I'm gonna try to fill in with the pin head technique.
Also revealed that I have a little bit more sanding to do with 2000 before I'm ready to buff. It's shinier, but shiny with scratches still...

[nvr2old]

If you go the route with the clear to fill your fish-eyes, make sure you have the hardener mixed with the clear before you do it. Sorry if that's a "duh" statement but I've seen people use that technique w/o the hardener and the drop of clear never dried. You might want to go with some 800 and a block, maybe even 600 to cut those fill-ins quickly..otherwise you'll never get it flat with 1000..then go over it with the 1000-1500-2000 again. I think I can still see 1000 grit scratches under you 2000. With a 2000 finish you should be able to see a glass smooth reflection. You may need to go over it with 1500 a bit more to get those 1000 grit scratches out and then finish up with the 2000. Looks like you have plenty of clear on there, so I wouldn't be afraid to take your 1000-1500-2000 over your body lines. That orange peel will stand out like a sore thumb on those areas if you don't. I'm proud of your patience and stick-to-it-ness..you're doing just fine.

[Sam 78 GS750]

OK, so pin head technique did the trick on the fish eyes. Took a bit to sand them down, but now it's smooth as glass. Got it all polished up. There are some imperfections still, but not bad for my first time painting a tank, and first time ever painting with a gun instead of spray cans. Ignore the bits of polish still on the tank...

20181217_083811 by samL9, on Flickr

20181217_083824 by samL9, on Flickr

[Sam 78 GS750]

Since then I got the new petcock on, put the tank on the bike, and fired her up. Started right up!

Seat's still at the upholsterer's shop, so I tied a couple of pillows together and took her around the block...I couldn't resist. Carbs need to be tweaked a bit, but it's running way better than I expected considering all that's been done to this bike.