78 GS 750 Rebuild

[pete]

Nice work Sam, Larry is an excellent coach and will get you sorted with a job far better than you think you're capable of doing

The only thing I can add with confidence is to do a +1 on a bit of filler with those pinholes, should sort them out nicely.

[LarsKroghStea]

Hi, read through the whole thread now. You have done an amazing job and you are much more thorough than I'll ever hope to be. I'm impressed!

[Sam 78 GS750]

Thanks Lars! I'd say your build is incredibly thorough and detailed as well. I've been following along, and can't wait to see yours on the road.

For me... Right now I'm sitting in primer, and I think I have the tank as good as I'm going to get it with primer and block sanding. Now I'm just waiting out the humidity to be able to get it in color and clear coat.

[Sam 78 GS750]

The humidity has been hovering above 90% for quite a while now, sometimes as high as 98%. Looks like I'll have a window between noon and 7 pm tomorrow where it's supposed to drop down to 60-65% humidity. Should be more than enough time to get to clear if all goes well.

There are 2 spots right next to each other where I got a little overzealous sanding with the 400, and there's a bit of a ripple. I'm thinking I can hit that 1 area with high build and sand it smooth right before I spray color...or would it be better to shoot the high build over the whole tank again? It's not too bad, and I could probably leave it, but I know it'll bug me if I don't fix it while I have the chance.

[nvr2old]

Hey, Sam. Not sure what you mean by bit of a ripple from sanding. Hmm. Did you block sand it till you started breaking through to bare metal? If not, I would maybe try that, and if that doesn't take it away just spot in a couple of coats on that area with some primer, let it set overnight, block it again and see if it doesn't fix the problem. No need to spray the entire tank again..although a (one coat) thinner mixture over the entire tank as a sealer before your base coat would be advised. Hope that helps.

[Sam 78 GS750]

So I sanded in long broad strokes over large areas. I stopped sanding when all the guide coat was gone in an area. I did break through to bare metal in some areas (even with the 400 grit), there's still plenty of primer in other areas. The area in question (against all advice) I sanded a couple of tiny trouble spots. Now the area around it is nice smooth and level, but those two spots are low.

I didn't break through to metal in that particular spot, but I did in the larger area if that makes sense. If I continue to sand that area, I'm worried that I'll make the problem worse because I'm already down to metal in spots. That's why I was thinking to just spray the area with high build and then block again.

I'll try to post pics in a few....

[nvr2old]

If you've already broken through to bare metal spots around the area you're talking about, yes, stop sanding. You've probably gone as far as you can and as you mentioned will start negatively affecting other areas. Just re-prime and block sand that low area again. You'll be fine.

[Sam 78 GS750]

I was able to take care of the trouble spot. I think I've got it as good as I'm going to get it. There are some small imperfections, but this is the point where I usually ruin good enough trying to get to perfect so I'm going to stop. I sprayed one more thinner coat over the whole tank like you suggested, and I've got about 10 more minutes to wait until I can spray color. Wish me luck!

[Sam 78 GS750]

Progress!

Color went on nicely. A little hair or something got stuck in one spot. I sanded it out, resprayed, and kept it moving.

Then came the disaster of the clear coat. I got 2 guns...one for primer and color, and another for clear. I had the color one dialed in nicely. The clear one, not so much. I was trying to spray wet coats, but not as wet as it came out.

To say I got a few runs would be an understatement. I have paint dripping on my garage floor right now. There's also some pretty big dust particles that landed in the clear.

Other than that it looks awesome though.

[Sam 78 GS750]

I'll post some pics tomorrow in the daylight. Maybe disaster is a bit of an exaggeration. I definitely have some sanding ahead of me, but it really did come out awesome.

[pete]

Glad to hear it Sam and looking forward to the pic's! I know the too wet problem, that's such an easy thing to do and I usually end up doing that myself.

When I did my 450 I didn't have my reasonably well sealed up shed, which meant I had dust and crud floating around and landing in the paint which wasn't great, but like you say most of it will sand out. The only painful part for me was the bits that landed in the white stripes *before* I cleared it without realising they were there... I can still see them...

[Sam 78 GS750]

So a bit of orange peel, a bit of overspray, and a few nasty runs, but all in all not too bad.

20180916_190100 by samL9, on Flickr

You can see the runs on top in this one.
20180916_190206 by samL9, on Flickr

20180916_190154 by samL9, on Flickr

Runs on the side
20180916_190122 by samL9, on Flickr

...and on the top.
20180916_190139 by samL9, on Flickr

...and of course, I had to throw it on the bike. Starting to look like an actual motorcycle.
20180916_191501 by samL9, on Flickr

[nvr2old]

Use 600 and a block to cut those runs out. Anything less and it just won't work. You don't have to worry about getting it so wet that it runs. It's easier to sand out a bit of orange peel then a run.

Look how straight your body work is, though. That's where all the block sanding pays off. Nicely done.

[Sam 78 GS750]

Note to self: It's much quicker and easier to scuff sand and spray more coats of clear if needed than it is to sand runs out of clear...

[Sam 78 GS750]

So the good news is that I was able to sand all the runs back. The bad news is there were air bubbles trapped in the runs and it looks pretty bad. After sanding back the orange peel with 1000 grit, I can see that they're in a couple other areas also. Google tells me it's "solvent pop" which seems to be reason #2 why it's a bad idea to lay it on in super thick coats.

I'm thinking I need to sand until they go away, which I hope doesn't mean sanding all the clear off.