Prepping motorcycle tank and fenders for paint?

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PostPosted: Thu Jul 22, 2021 3:57 pm
Hi everyone! I'm new to the forum and just trying to get my feet wet again with some auto body work and painting. I did a bit of back yard body work as as a teenager in the 1960s and painted my Honda CB750 in the late 70s... I'm thinking I probably used Dupont Centari (?) or perhaps it was Dulox (?) on the 750. It looked pretty good but was never a show winner. It now has a few chips here and there; but overall the paint and finish has held up pretty well. I'm now a retired old-fart trying to rekindle whatever such skills I may have had way back then and I've discovered a lot has changed!

One of my bucket list projects is a Volvo P1800 restoration that's now on a rotisserie. The car needs a lot of rust related metal work and before going any further on it, I thought I'd get some practice on a 1973 Sportster I've had for a long time that needs some of the same long neglected skills.

This will be my first stab at the BC/CC process and I'm currently just feeling my way along. I've decided on the color (GM 43, WA177B, Emerald Green Metallic) and perhaps a bit of GM 55A or similar Gold accent striping, I have not yet decided on the brand or level of paint. I've been poring through the PPG Deltron & Shop-Line PDSs, as well as the Sherwin-Williams Ultra 7K and ATX PDSs. Mostly because both brands have shops that are relatively close by.

But right now, I'm looking for some help and guidance with preparing the Sportster tank and fenders for paint. And I may have already gotten ahead of myself. As the pictures show, I started with welding a patch on the top of the rear fender where it had cracked at the seat's rear attach point. When I got too aggressive with the MIG machine and blew through one of the corners I fabricated another patch to fix that.
Skins-3.jpg

Then, not knowing some of what I've only recently discovered, I stripped and sanded (most) everything to bare metal and proceeded with applying body filler... over the welded patch and a few other dings... directly on the bare model as I would have back in the day.
Skins-2.jpg

Now I understand the preferred sequence with such a bare metal project would be to start with an epoxy primer over everything.. then any body filler goes on top of that... then high build primer surfacer... perhaps a sealer... followed by the BC and CC.

My question is... How should I proceed from here? Should I grind out all the body filler to bare metal to epoxy prime everything and then reapply the body filler? Or can I epoxy prime all the bare metal up to and as close as I can get to the existing body filler.... let it all cure and sand and apply the hi build primer surfacer? Or of course any other suggestions or advice anyone may have!

Thank you! ZT

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PostPosted: Thu Jul 22, 2021 6:11 pm
The preferred way is strip/media blast metal to remove all rust and old paint.
Clean and apply 2 coats of epoxy primer. I use the black mainly and let it cure at least over night.

At this point you can lightly block sand the epoxy and it will act like a guide coat, revealing the low spots that may need some filler.

That being said, you can also strip/media blast to clean metal and then apply filler such as you have done. Clean with automotive grade wax and grease remover and let flash 30 minutes (while your epoxy induces) and then spray your epoxy primer coats over the metal and filler.

Depending on the condition of your metal, you could just use epoxy primer instead of build primer. Block sand to see if you have any low spots, if so, shoot more epoxy primer and then sand again, etc.

In the Members Projects Section you can find where others have painted motorcycles and see what steps and materials they used.

Here's a fuel tank from a 2000 Harley Ultra Classic I painted:
SPIBlack.jpg

SPIBlack1.jpg
1968 Coronet R/T


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PostPosted: Thu Jul 22, 2021 7:48 pm
'68 Coronet R/T wrote:The preferred way is strip/media blast metal to remove all rust and old paint. Clean and apply 2 coats of epoxy primer. I use the black mainly and let it cure at least over night.

At this point you can lightly block sand the epoxy and it will act like a guide coat, revealing the low spots that may need some filler.

That being said, you can also strip/media blast to clean metal and then apply filler such as you have done. Clean with automotive grade wax and grease remover and let flash 30 minutes (while your epoxy induces) and then spray your epoxy primer coats over the metal and filler.

Depending on the condition of your metal, you could just use epoxy primer instead of build primer. Block sand to see if you have any low spots, if so, shoot more epoxy primer and then sand again, etc.

In the Members Projects Section you can find where others have painted motorcycles and see what steps and materials they used.

Here's a fuel tank from a 2000 Harley Ultra Classic I painted:

Thanks 68Coronet! I appreciate your reply. I also enjoyed reading and learned a lot from your sticky thread on guide coats.

I now understand the reasons and logic that supports going with the "preferred method". But, "with that being said", if I proceed as is with what I have... clean with wax & grease remover, then epoxy prime... is the only downside the lack of corrosion protection under the existing filler? Or might there be other issues?

For some reason, I had recently formed the apparently mistaken impression that epoxy primer shouldn't be applied over filler. But, if I'm not mistaken, you dispelled that notion in your guide coat sticky! Is that correct?

Please also explain and expound a bit on...
"Clean with automotive grade wax and grease remover and let flash 30 minutes (while your epoxy induces) and then spray your epoxy primer coats over the metal and filler."

Can you recommend a specific cleaner or type of cleaner. With your mention of 30 minutes of flash time, I'm thinking you must be talking about something other than a fast evaporating cleaner. Is this cleaning process supposed to be doing something more than simply cleaning the filler surface so as to make it a more suitable (or acceptable) substrate for the epoxy primer?

And, "While your epoxy induces"... I'm not at all familiar with this! Is this something that's supposed to happen after mixing the epoxy primer and left to sit for a bit, before it's sprayed?

And by, "Depending on the condition of your metal..." Do you mean if my filler work wasn't quite up to snuff, I may need a high build primer to bring up the low spots rather than more coats of epoxy?

And is a high build primer any better or worse a substrate for the BC than epoxy primer? And, in either case, would a sealer be recommended before spraying a dark metallic green BC?

And, BTW, your Ultra Classic tank is awesome! Is the Harley emblem a decal above the BC and below the CC?

Thanks again for your thoughtful reply!
I do appreciate your help! ZT

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PostPosted: Thu Jul 22, 2021 8:24 pm
Best rust protection is epoxy first.

I use a Wax and Grease remover that is forbidden to be mentioned on this site. (long story) Anyway, the best method is to put some in a spray bottle and apply it to the panel. You will immediately wipe it off with a clean towel. The idea is to remove the contaminants while they are in solution. Once the surface is clean you wait 30 minutes or thereabouts to make sure any solvent that might be trapped in your filler has time to escape.

Epoxy primer usually requires a little induction time. You mix part a & b and then let it sit.
Personally, I have used it immediately after mixing without any issues but I do mix it very well.

Epoxy can be applied under and over filler. I think it's etch primer that has to be applied over filler but not under it.

If your metal already looks good, without any waviness or indentations, you can just use epoxy primer. I believe that's what Darrelk did on his Charger truck build.

Generally you will apply epoxy, do filler work, (some seal the filler with epoxy) then go to the 2k build primer, guide coat, wet sanding process.

When spraying 2k build primer, you want to give it plenty of flash time between coats. Rushing can trap solvents and cause issues.

The emblem was attached firmly to the tank with adhesive. I left it on and painted around it.

FuelTankRight.jpg
1968 Coronet R/T


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PostPosted: Thu Jul 22, 2021 10:32 pm
'68 Coronet R/T wrote:Best rust protection is epoxy first.

I use a Wax and Grease remover that is forbidden to be mentioned on this site. (long story) Anyway, the best method is to put some in a spray bottle and apply it to the panel. You will immediately wipe it off with a clean towel. The idea is to remove the contaminants while they are in solution. Once the surface is clean you wait 30 minutes or thereabouts to make sure any solvent that might be trapped in your filler has time to escape.

Epoxy primer usually requires a little induction time. You mix part a & b and then let it sit.
Personally, I have used it immediately after mixing without any issues but I do mix it very well.

Epoxy can be applied under and over filler. I think it's etch primer that has to be applied over filler but not under it.

If your metal already looks good, without any waviness or indentations, you can just use epoxy primer. I believe that's what Darrelk did on his Charger truck build.

Generally you will apply epoxy, do filler work, (some seal the filler with epoxy) then go to the 2k build primer, guide coat, wet sanding process.

When spraying 2k build primer, you want to give it plenty of flash time between coats. Rushing can trap solvents and cause issues.

Thank you kindly again 68Coronet!
I appreciate your informative replies.
ZT



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PostPosted: Sat Jul 24, 2021 11:55 am
sorry i didn't read through all this. but your perfectly good to epoxy what you have in the picture as long as its clean and dry. make sure the w/g remove has evaporated completely .
Jay D.
they say my name is Jay



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PostPosted: Mon Jul 26, 2021 5:09 pm
badsix wrote:sorry i didn't read through all this. but your perfectly good to epoxy what you have in the picture as long as its clean and dry. make sure the w/g remove has evaporated completely .
Jay D.

Thanks BadSix!
I appreciate your reply and your advice.
ZT

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PostPosted: Tue Jul 27, 2021 12:07 am
they say the hardener for filler will flash rust bare metal,
some say their filler is safe over bare steel,
who knows what to believe,

what i do know is filler should go over grinded steel, 36 grit 2" or 3" disc,
glazing putty is alright over 80 grit steel as far as adhesion goes anyway.

yes 100000000000 people will tell you they put filler over 80 grit steel, but if you look close it does not hold well or feather well, period.

your bike will be fine either way,
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PostPosted: Tue Jul 27, 2021 11:52 am
Thank you Dave!
I appreciate your reply.
ZT

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