78 GS 750 Rebuild

[Sam 78 GS750]

Obviously I have to hit the underside a bit better, but am I being overly cautious on the rest? I'm thinking leaving any rust would be a bad idea. What you can't see in the pics is that there are spots where there's some pitting, and tiny spots of rust at the bottom of the pits...

I'm thinking I should be safe to use Ospho on the underside, since there won't be any filler there. I'm wondering if I can spot treat the trouble areas on the rest of the tank and then clean it thoroughly and maybe re-sand and not have issues with filler over the acid treatment.

[Sam 78 GS750]

I hit the tank today with my random orbital sander, roloc discs on my drill, and sandpaper by hand... It's better, but I still don't feel warm and fuzzy about putting body filler on top of it or painting just yet.

This was after a bit of sanding
20180801_003521 by samL9, on Flickr

and underneath. again, after sanding for a bit. I'm kicking myself for taking it back like this, but I figured it would come off fairly easily. This seems like way more than flash rust from sitting in the shop for a couple of days before I picked it up.
20180801_003815 by samL9, on Flickr

How it sits now after a good while working on it. Like I said, much better but still questionable in spots.
20180802_201954 by samL9, on Flickr

20180802_202058 by samL9, on Flickr

20180802_202122 by samL9, on Flickr

and underneath
20180802_202153 by samL9, on Flickr

20180802_202211 by samL9, on Flickr

[Sam 78 GS750]

I am a bit stumped on where to start though. Like I said before, the radiator shop let my tank sit before letting me know it was done. There's quite a bit of surface rust. Most of it I can sand, but some I can't like behind the tank badge area. I had planned on using Ospho.

I picked up Evercoat body filler, and the paint rep said phosphoric acid would be fine under it. I called the Evercoat hotline to confirm though and their rep said phosphoric acid is a no-go under their fillers. She wouldn't recommend another rust converter either...

What a rep on a hotline can/can't recommend and what works in the real world is sometimes different though...

Is there another rust converter I can use under this filler and be ok, or is there a filler that you know won't have issues with phosphoric acid?

[Sam 78 GS750]

Skim coating the entire tank is not a bad thing. Maybe start with filling the deepest dents and dings first with one application, then follow that up with a thinner coat over the whole tank. It'll give you the desired final appearance. You've done such nice work on your bike to this point, it deserves the commitment. The first thing people will notice is the body work and paint. It sets the bar for the whole project.

I'll try that. I had planned on just skim coating everything from the start, but it makes sense to tackle the trouble spots with one coat then another all over.
I definitely understand what Pete was talking about at one point in his Kat thread about leaving paint for last. Since I'm so close to finishing the project, there's definitely the temptation to rush through this. It would be a shame though... I've spent great attention to detail on the cosmetics of things no one will ever see. Why do a half ass job on the most important cosmetic items. Especially since I sprung for top shelf paints and materials...

[nvr2old]

Skim coating the entire tank is not a bad thing. Maybe start with filling the deepest dents and dings first with one application, then follow that up with a thinner coat over the whole tank. It'll give you the desired final appearance. You've done such nice work on your bike to this point, it deserves the commitment. The first thing people will notice is the body work and paint. It sets the bar for the whole project.

[Sam 78 GS750]

...oh well. Onwards and upwards. Either way, the coating looks good inside.

I sanded the outside a bit with a block to see what I'm dealing with. Looks like there are a quite a lot of low spots and dings in addition to the dents and dings I know and love, and am intimitely familiar with after owning the bike for 10+ years lol. I'm thinking I'll just do a skim coat of filler over the entire tank. I'd like to use Ospho on the rust, but I've read bad things about phosphoric acid under body filler, so I'm going to wait until I talk to the guy at the paint store when I buy everything today or tomorrow.

[Sam 78 GS750]

So I got my tank back from the radiator shop yesterday... Not 100% pleased. Their website showed that they were a Gas Tank Renu place, which had great reviews online. Their website shows a red interior coating. What I got back is white, which makes me think Kreem... They also didn't call when it was done, so it sat in the shop for a few days. There's quite a bit of surface rust. The coating's also covering the petcock threads. I'm hesitant to use a thread chaser/tap there, but I may have no choice

[pete]

As long as you spend the time getting the prep work right, your paint will be fine, it's the easiest part

You'll only learn by doing though, and for a first time just be prepared to get something wrong and needing to re-do it. Nothing wrong with that, just be patient and don't expect perfect results first time out.

[Sam 78 GS750]

I found that out after a bit of wasted effort, Pete. I was able to get some smaller plastic pieces looking pretty good with plastic polish, but these were too big and too far gone I think.

I look at everything like this that I have to paint as practice for when I paint the tank, side covers, and tail piece. It's a bit of a daunting task for me... Hopefully I can get them looking half as good as you did with your Kat.

[pete]

Nice work Sam! Cleaning up plastic bits without painting is tough... especially when it gets that faded/used look.

[Sam 78 GS750]

this build of yours is literally insane.

Why thank you kindly, sir.

I'd love to buy it when your done lol

NOT FOR SALE!

lol

[GabrielGoes]

this build of yours is literally insane. I'd love to buy it when your done lol

[Sam 78 GS750]

320 sandpaper, a couple coats of primer, a wet sand, and a couple coats of semi gloss black later. Not perfect, but much better than they were... I was bound and determined to keep them as bare plastic, and just get the gouges out and polish them. I was thinking it would be much easier to maintain than if I painted them. It just wasn't in the cards though.



20180714_185930 by samL9, on Flickr


20180714_185852 by samL9, on Flickr

[Sam 78 GS750]

hmmm... plastic polish isn't cutting it... 320 and semi gloss it is.

[Sam 78 GS750]

...in other news, I made a mess of my inner fenders and chain guard trying to get some deep scratches and gouges out. The gouges and scratches are out. Now I need to get the sandpaper marks out. Right now, I'm thinking they weren't so bad how they were...