How do you prep your frames?

I was wondering on everyone preps their frames for painting? On my K5 mini trail I just sent it to get powder coated but on my K1 CT70 I’m torn about getting it sand blasted first. The guy that painted my mini did a great job but I don’t think he would get “deep down” in the frame of my 70 so I was gonna get it sand blasted and primed myself before I send it to get painted. Should I use another method besides sand blasting? Any and all info is greatly appreciated.

My 73 Mighty Green ST90 got sand blasted down to bare metal inside and out. The few rust pitted areas then got a touch of Bondo and sandpaper followed by primer filler and the green color coat. The clear went on after that and I'm still happy with the outcome years later.

Rick

Good to know b52bombardier1 I was concerned that the sand might be too much.

You can get away with using sand, steel grit, garnet abrasive, even aluminum oxide. IMO, the best media is glass bead. It can be slower than the others just mentioned. However, it removes virtually zero solid metal and leaves behind the optimal surface finish...clean, "white" metal, with no "profile" , i.e. sandpaper-like texture.

I agree with Rick's prep method, filler applied directly to bare metal. That allows optimal bonding. In warm ambient air temps, scratch filler (all that it needed to fill rust pits) will set quick, can be sanded then sealed with epoxy primer-sealer within 24 hours. Applying an extra coat, or two, over the filled areas allows for shrinkage. I like to give the primer & filler 48-72 hours to cure, outgas & shrink, before final blocksanding. A week is even better.

If you're going for perfection, be prepared for a second round of scratch filler & fine blocksanding. Small imperfections cannot be seen until the part (especially a frame) is one, uniform, color...and viewed with low-angle lighting. More accurately, I'm talking about the little stuff that becomes an eye magnet only after the bike is assembled.

when I did mine. I sand blasted first. then had to cut out a couple spots that blasted thru. replacing with fresh metal. used epoxy primer to seal it then did light body work prior to painting primer then base clear.if you can spray primer I would just try painting yourself. not a lot of super flat surfaces to mess it up. base clear is pretty forgiving. just be careful not to sand thru the clear if you decide to color sand and buff. painters can get kinda pricey. for some of their prices you can paint it and if you mess it up you can do it again for less.

The main thing is, can you do it safely to protect your lungs.

mark from florida said:

when I did mine. I sand blasted first. then had to cut out a couple spots that blasted thru. replacing with fresh metal. used epoxy primer to seal it then did light body work prior to painting primer then base clear.if you can spray primer I would just try painting yourself. not a lot of super flat surfaces to mess it up. base clear is pretty forgiving. just be careful not to sand thru the clear if you decide to color sand and buff. painters can get kinda pricey. for some of their prices you can paint it and if you mess it up you can do it again for less.

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Pinholes, or worse, left behind can be worriesome; it all depends upon their location(s) and size/total acreage. They're not all that common and of what's come across my bench, most were the inner heatshield and lower rear wheel arch...battery electrolyte (acid) damage.

Bodywork has indeed gotten expensive. A boatload of new regs went into effect in 2006. Corporate mergers eliminated competition, within the past 4-5 years. The cost of automotive paints, along with everything needed to actually use them, have at least quadrupled since 2001. Some materials have taken stratospheric increases. For example, mineral spirits went from $3.00/gallon to $14.00; a drum of glass bead blast media went from $16 to $75...and the drums are smaller. Start-to-finish, a typical K0-K3 frameset takes 25 man-hours to complete...minimum. If there's substantial damage repair involved, the 40-hour mark is easily reached. Just a little math will tell you why the costs are what they are...and how much a motivated DIYer can earn in "sweat equity".

The middle ground, at present, is a basecoat/clearcoat paint system, using a catalyzed clear top coat. That can give very good results and allow one to keep the project total under $300. Basic airdyr/rattlecan enamel can turn out very well, too. It's not as durable but still superior to what was used 40-50 years ago. Enamel can be colorsanded & polished to great effect, given some time (usually weeks) to fully harden.

Most important element of any refinishing job is the prep. Get that right and a great result is possible.

As mentioned earlier a respirator and I use a cheap Tyvek suit ,I get my media at tractor supply the red bag which is a little finer for $10 I live in the southwest so I really don’t have to deal with lots of pitting and rusting like the rust belt people do ,these frames That were given to me we’re just about perfect ,I Use a two part Epoxy I didn’t sand the Epoxy and lay down cloud silver, basecoat and clearcoat if you know your gun good which I’ve painted over 40 forklifts the end result you won’t have to color sand

The epoxy primer that I use does not have to be sanded either if the next application is applied within twenty-four hours. After that, you must scuff it to create a mechanical bond between applications. Applying the basecoat within that time frame allows for a chemical bond.

Yes, definitely get a NIOSH-approved cartridge mask. These paints generally contain an isocyanate type of chemical which is horrible for our lungs.

Rick

That gray primer looks a lot like the PPG "epoxy primer" I used years before this board was created. The stuff was high-build, flowed-out like glass, and was super-easy to sand, if needed. It would also soften & dissolve in reducer, days or weeks after application, which had me (and a number of others) wondering just what this material is. A catalyzed epoxy should withstand just about any chemical other than methylene chloride. It's good as a primer-surfacer, not so much as a primer-sealer. True epoxy primer-sealer, is impervious to most chemicals...and a tough S.O.B. to sand.

Whether, or not, to sand primer depends upon the project...and painter discretion. It's not strictly necessary. However, the best epoxy primers don't flow-out very well. With a true candy color, the end result won't look quite right if there's any orange peel left in the primer. I've always gone over framesets, giving them a final blocksanding with 600-grit. A lot of little stuff can't be seen until a part is one, uniform, color...and most flaws can be eliminated with this added step. It's an extra prep stage and optional, especially with any conventional metallic or solid color, except gloss black...maybe. If one has perfectionist tendencies, the difference a final sanding makes is substantial; the parts have a clean, crisp, look. It is another full day's work and it's drudgery...so not for everyone.

As for breathing protection, isocyanates are seriously toxic, nothing to take lightly. If you have access to a state-of-the-art downdraft spray booth, then an isocyanate-rated twin-cartridge respirator is okay. IMO, getting and maintaining a perfectly airtight seal against ones face is difficult. I invested in a fresh air supplied full face mask, positive pressure doesn't rely on a perfect seal...plus a full paint suit. And this is with a crossdraft booth setup. Some may think that I am obsessive about this topic. Know that methylisocyanate causes suffocation at the cellular level, and catalyzed paints based on this chemical remain "wet" more than long enough to be inhaled while still wet, then will harden(!). These paints are top-quality, extremely durable and non-toxic...once cured. Just make well-informed decisions. In this case, it's all prevention...no cure possible if you get it wrong.

Reading the manufacturer's tech sheet will tell you everything about the chemistry & safety protocols.

Years ago my mom came down with pulmonary fibrous for reasons unknown. I went out and bought a Hobbyair system https://axispro.com/index.php?l=product_list&c=1 after I saw what all she went through- it would still be cheap at twice the price..... Remember if you can smell the paint you are breathing it's vapors and this applies days later as well.

I think I could build one of those...
Clean shop vac- grinding shield- piece of canvas- long shop vac hose- cardboard box- utility knife and duct tape.
Hillbilly respirator :--)

kirrbby said:

I think I could build one of those...
Clean shop vac- grinding shield- piece of canvas- long shop vac hose- cardboard box- utility knife and duct tape.
Hillbilly respirator :--)

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I bet you could, and I've long admired your resourcefulness. That said, for a number of reasons, this is one piece of equipment where it pays to just make the investment up-front.

The cardboard box would of course be the air regulator. The canvas and shield would make the hood. (Just didn't want you to think I'd be wearing a box on my head)

All is very good info!!!!!

kirrbby said:

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Some things just shouldn't be repurposed...

Isocyanates in paint aren't only about breathing them in either. Can be absorbed through the skin and eyes just as easily. Any home sprayer should be using a breathing system and full body protection. If you see the guys on TV spraying inside a professional booth that has the proper filtration and ventilation system and are still wearing a full mask and suit that should tell you something.