Hello,
Been having some interesting times with my new '86 K100 project. First, decided that I would have the frame blasted and powder coated. That came out well as I just retrieved the frame this morning. From when I dropped it off til I picked it up it was 8 days and USD $240. My friend, Greg, who has a small shop says that's not a bad price in this area, S.F. Bay Ca.. And that he's used to paying as much as USD $800. for a complete job, i.e. frame, engine, tranny etc. For anyone in this area who is interested, the shop was MelRose in Oakland. And I do recommend them. Didn't know there were so many shades of black. But I picked the shiniest and it seriously looks good. Now to make the rest of the restoration look as good.

Second, started working on the gas tank. The tank has/had 4 dings. Two of which I partially banged back out. Small dings or any too difficult to reach on the inside I think will be body puttied. Which leads to my next problem. It may be California's environmental laws or just BMW's paint jobs but using what I was told is the highest quality stripper available to me, Airplane stripper, I've found that the stripper doesn't remove all the previous body putty, primer, paint combination. The stripper advertises that it is readily capable of removing even epoxy paints. But after 4 applications I've still got small specks and bits of body putty and paint left. At one point I applied the stripper thickly slathering it on using a brush. And then spraying it with I high pressure water sprayer  which peeled much of the paint off as the water jet got under the edge of the painted area.  But It left behind small bits that I can only remove with a razor. My last effort was to apply plain acetone and scrub with a plastic scrubber. The acetone cleaned off some stains but didn't seem to faze what appears to be body putty. Anyone else had this problem or know of a product suitable for removing the paint? I'm thinking of a ride to Nevada to get some stripper untrammeled by Calif. law. Just to see what it takes. Any home brew concoctions for paint removal? I'm not willing to use heat as that could/would damage any coatings on the interior. Any comments (helpful) or other suggestions?

thanks
J

Are there coatings inside the tank? There weren't any when it left the factory. A heat gun and some Scotch Brite should get the stuff the stripper leaves behind.

Over here the big brand household paint stripper is Nitromors. This used to be good, but then lost its edge with regulation and no longer shifts stuff like it used to.
I now buy the 'trade only' stuff and find that it will easily remove the OE paint from the tank, and engine casings too. Don't skimp, and you have to follow up and do the spots, but they come off easily enough by the second or third go. I've found it softens body filler too so that it can be scraped away quite easily.
I daub it on heavily with a paint brush, leave it undisturbed (I think that bit's important - it never seems as effective if you keep sloshing it around with the brush), then brush the sludge away with the same brush. Afterwards, I wash it down with hot soapy water - but watch the fumes at this stage as the heat seems to give things a real kick and I once made myself poorly doing it indoors, even with ventilation.
As said, Scotchbrite is always handy.

Point-Seven-five wrote:Are there coatings inside the tank?  There weren't any when it left the factory.  A heat gun and some Scotch Brite should get the stuff the stripper leaves behind.  

I'm not sure. Just looking in I can't tell due to the discolorations. I've been seriously disappointed in the available strippers. Think there are three brands immediately available in this area, auto parts house and hardware store. The "airplane" brand came from a paint store that supplies the auto trade which is why I thought it would be the best. Think the tank has been repainted and possibly repaired at least once before. In the four times applying the stripper I tried applying it, leaving it over night and then buffing the tank with a bench mounted wire wheel. Might be worth trying the heat gun and Scotch Brite. The wire wheel made some serious marks in the aluminum.

There are 3M paint stripping discs that fit to 4" angle grinders. You need to check on the suitability for using on aluminium.
Regards Martin.

I have found that aftermarket paint isn't as tough as the stuff they use at the factory, probably because the factory can justify the cost of the procedures for controlling the environmental discharges. It should be easier to strip.

I have had some success with Easy Off spray oven cleaner spray. Shoot it on and cover it with wax paper and let it sit for a couple hours. Scrub it with ScotchBrite and rinse with Lots of water followed by a wipe down with distilled white vinegar.

Being thin, soft aluminum I would avoid using anything more aggressive than ScotchBrite. Abrasives and wire wheels are too rough on the metal in my opinion.

Prime with a self etching aluminum primer before doing any filler. I have found that gives the filler a better grip.

Point-Seven-five wrote:
I have had some success with Easy Off spray oven cleaner spray.  Shoot it on and cover it with wax paper and let it sit for a couple hours.  Scrub it with ScotchBrite and rinse with Lots of water followed by a wipe down with distilled white vinegar.

Being thin, soft aluminum I would avoid using anything more aggressive than ScotchBrite.   Abrasives and wire wheels are too rough on the metal in my opinion.

Prime with a self etching aluminum primer before doing any filler.  I have found that gives the filler a better grip.

I'm rather uncomfortable with the use of Easy Off as I believe the active ingredient is Sodium Hydroxide. From the net: Sodium aluminate is also formed by the action of sodium hydroxide on elemental aluminium which is an amphoteric metal. The reaction is highly exothermic once established and is accompanied by the rapid evolution of hydrogen gas. The reaction is sometimes written as: 2Al + 2NaOH + 2H₂O → 2NaAlO₂ + 3H.


But I would agree with use of ScotchBrite. But the wire wheel has made etching marks in the aluminum. Not sure if that's bad or just a "so what". It may give bondo body putty, primer and paint something to grip to as aluminum  has some notoriety as being difficult to adhere to.


We probably need a howto thread about what works best for cleaning and repainting our bikes. There are several different materials in the bikes each with different requirements and that list seems to change by model year. Plastics and fiberglass are particularly a concern. And then there is the fact that different products are available in different locations/countries. Just a thought as I work my way through this project.

jjefferies wrote:Any home brew concoctions for paint removal? I'm not willing to use heat as that could/would damage any coatings on the interior. Any comments (helpful) or other suggestions?

A heat gun will do. Don't be afraid. The tank is used for boiling fuel. The OEM tank interior is bare aluminum. If it were coated with something, a heat gun wouldn't affect it.  

Did you do the paint sanding step? The product being used by this person is Safe-Erase. Start at around 2:48 unless you like foreshadowing music.

Interesting video, though he did skip a few details like removing the gas pump and fuel filter and use of a paint hardener. Yes I did the preliminary sanding but unfortunately the paint did not respond in the manner shown in the video. Again I'm wondering if it is California's environmental restrictions on paint and other chemicals which is the cause. My previous foray into painting, over ten years ago was not as difficult as the current one. After reading over the several comments, I did try the heat gun but after hearing the tank ping in various manners as I was heating it, I gave that approach up. Just a little chicken about damaging a tank which already has several major dings and other unknown damage. My final choice was 220 grit wet/dry sandpaper and a lot of elbow grease. I am not painting the bottom of the tank but getting the old paint and body putty from around the welded edges is proving a challenge. And again due to environmental regulations use of hardeners and shooting out of doors is a problem. At this point it's looking like rattle cans are going to be the approach although I do have all the equipment to shoot paint old style. I have two guns, compressor, breathing air supply and other tools. But shooting with a hardener which was not addressed in the video forces you into a hard choice given the current laws here. There is a new spray/rattle can which allows you to mix a hardener with the paint. Somewhat costly but cheaper than the other  requirements. This according to the auto paint store that I've been doing business with for the past 10-15 years. Thinking about a ride to Nevada .

In Briz we have a couple of places that will hire out their spray booths. One is $180.00 for a day and do it yourself, or you can also hire a professional painter for $90.00 per hour. A couple of mates are looking at getting their bikes done this way. They will prep and remove the body work and supply the 2 pack paint and then get the painter to do the paintwork. As both their bikes are the same colour they can get them done in one hit. One guy was looking at a paint respray of $1500. Try seeing if you can get a local paint shop to do the tank.
Regards Martin.

He is using a compound with dichloromethane in it; the paint reaction is very typical of that (rather nasty) stuff. It's also banned in the UK for domestic use, unless you specifically go a trade dealer.

The 2-pack rattlecan is quite good but suffers from a very limited shelf life. Once you've pulled the trigger I think they give you about two days to use it all, but IIRC our dear old Laitch made his last a week by introducing it to the fridge. The alternative - which I can vouch for as creating a very hard finish - is cellulose rattlecan colour followed by 2K acrylic laquer

https://www.rsbikepaint.com/en-gb/datasheets/2klaqnoniso-instructions.pdf

Somebody over there has got to sell it. From experience: follow the instructions exactly and only use light coats for the lacquer, allowing 8 - 24 hours between coats to completely dry.

http://www.simpilot.net/~sc/brick3/83b.png

After it's been polished but before I waxed it.

Dai wrote:He is using a compound with dichloromethane in it; the paint reaction is very typical of that (rather nasty) stuff.

IIRC our dear old Laitch made his last a week by introducing it to the fridge. 

If by He you mean the guy in that video, what he's using has no methylene chloride in it, according to its MSDS.

If you're referring to rattle-can spray life, you are R-ing incorrectly. I don't paint my moto; I don't want it to be too attractive.

I have used that 2K rattlecan clear coat on a couple of projects. Putting the catalyzed paint can in the freezer and letting it come to room temp with a little help from a soak in warm water before reuse lets me keep the paint usable for a week, maybe a bit more.

I allow 5-10 minutes to flash between coats. 3-4 coats with one or two light additional coats focusing on edges where I'm afraid I might sand or rub through the clear.

Point-Seven-five wrote:I have used that 2K rattlecan clear coat on a couple of projects. 

The reference to "2K"? Am I missing or not remembering a manufacturer?

jjefferies wrote:

Point-Seven-five wrote:I have used that 2K rattlecan clear coat on a couple of projects. 

The reference to "2K"? Am I missing or not remembering a manufacturer?

It's the stuff mentioned in Post #11 and a link given to it.

It's the two part clear that has the catalyst in the bottom of the can. You activate the paint in the can by pushing a big red button on the bottom that punctures the divider and allows the two part to mix. 2K refers to the fact that you mix two parts together. It the type of paint. not a trade name.

Laitch wrote:If by He you mean the guy in that video, what he's using has no methylene chloride in it, according to its MSDS.

Ah. It's the H2-02 doing the damage then. Impressive.

Dai wrote:Ah. It's the H2-02 doing the damage then. Impressive.

Maybe it's a special H atom like the one used in Jack Daniels.

jjefferies wrote:The stripper advertises that it is readily capable of removing even epoxy paints. But after 4 applications I've still got small specks and bits of body putty and paint left.

Yeh! just found that a Dremmel tool with buffing wheel works well to get these small problems. And you can buy the buffing wheels by the 10's online. Just it's not exactly the quickest or most efficient way of removing small bits.

Couple of points on paint removal - 1. stripper likes a bit of time to work. leaving it overnight helps but it tends to dry out. works better if you can put stuff in a plastic bag or clingfilm.
Also - alternatives to paint stripper - Brake fluid might shift what stripper doesn't
Cheers
Steve