Topic: side cover stripping question

[pelicanwheel]

Hi everyone.  I've been ebaying the heck out of NOS parts for my "10 year in the making" complete restoration of my '76 cb750.  It's taken 10 years because somewhere along the way a wife and three kids snuck in!  I'm almost ready to start getting my crap together and get this done, hence all the buying on ebay.

I bought the paint kit from don the dirtbike guy, and sourced several decent left side covers.  I'll use the best one.  My question to the board is what is the best way to strip the old paint off the covers?  The reason I needed a new left cover in the first place was because I used stripper on my original and when I went to scrape it off, the plastic came off with it.  So now I have a non-cracked '76 left side cover with a ton of nicks in it!

As for the restoration...I've had just about all aluminum parts chrome plated (all but the engine fins around the pistons).  The forks, engine covers (after market aluminum that is chrome plated), the hubs for the wheels and associated parts, levers, and just about ever thing else shiney was chrome plated.  I had all the painted objects powder coated (Glendale Power coaters in Arizona - extremely reasonable - about 250 bucks for frame, swing arms, center stand, kick stand, handlebar clamp, triple tree, and a bunch of other tiny stuff (foot pegs, etc).  That price includes all prep work - write me for contact info if you like).  I even have new rims from 10 years ago, that I never laced.

Finally, I rebuilt the engine myself (10 years ago) where I stripped and repainted the engine casing.  The engine looks brand new (though I can't remember which paint I used...I just remember that I had to cure it in an oven).

So my two questions are:

how to strip the plastic covers

and has anyone ever chorme plated the carb bodies?  I've done the float bowls, but would like to do the bodies as well.

Also, the bike is still totally disassembled, so if anyone would like to know what certain parts look like chrome plated or poweder coated, let me know and I'll snap a photo.

thanks,

Pelican

[Bob Wessner]

I have a similar question re: side covers. The PO rattle can painted them black over the original and even did a bad job of that. I was thinking I would have to resort to sanding the paint layers off carefully, ugh, the covers have louvers. Haven't started yet so I'll see what other responses you get.

[cbjunkie]

my response is...good question!

i've been mulling over this one, too... 

[clarkjh]

Pressure washer , thats how I stripped mine.  Or I should say I washed the bike after a ride with a pressure washer and it stripped the paint from the tank, side covers, part of the faring and sadle bags.

Low pressure bead blast?  Small "pick" to flake the paint off.   Or the old elbow and sandpaper/beer treatment.

James

[malcolmgb]

just a thought - they say don't spill brake fluid on a painted surface it will remove the paint and I don't think it will attack plastic.

[Bob Wessner]

just a thought - they say don't spill brake fluid on a painted surface it will remove the paint and I don't think it will attack plastic.

Hmm, anyone ever actually tried this? Hate experiment with my only set of original side covers.

[pelicanwheel]

hmmm...brake fluid...hmmmm

Since I have the original screw up cover, I'll try that (tomorrow)..stay tuned!

(again, what a shame a perfectly non cracked left side cover is being used as a guinea pig!)

[Zane]

My little 400f side covers aren't as large or as complex as the 750 panels, but I think they're all made from the same sort of stuff, aren't they?

Whatever, I sandblasted mine first, then I wet sanded them with a 400 grit paper.  Then I filled them with 2 part marine epoxy.  Then I sanded with a 400 - 600 - 1000 - (and if I had it) - 2000 - progression.  The insides I did with about a 320 only.

I think blasting them works great, but I'm very careful, especially along and around corners and edges.  On the flatter areas it's pretty easy to get a smooth blasted job done, but edges and ridges need to be tackled with the proper angle of blast, or else you get a kind of funny, roughing effect where the plastic comes to the corner.  I found more passes with the blast from further back and with the focus straight on to the corner or edge worked best for me.  And sorta long sweeping motions - more like you were actually painting it with the blaster, not stripping it.(I practiced a little the first time on the back of the inside of the grommet hole on my covers.)  

I had some old side covers that were painted at least 6 times and never stripped.  (I almost left one "natural" after blasting it because it really looked - it looked like psychedelic man.)  I'm happy once I get down to the original red primer, and don't have a problem leaving that red - as long as everything is smooth.

This one here is a spare I've been bringing along when I have time.  The grey stuff inside the top holes is JB Weld.  I've found  reinforcing that section a little, on the left side cover for my bike to be prudent.  Because it is not as easy to remove as the right side cover (you've got to kind of wedge it up under the hinged side of the seat to get it removed from the bike) they mostly break there.  So they're harder to get and they're more expensive (used) generally, than the right side.  I'm sure your particular side covers have their own, similar quirks.

The bottom line, I think, is that sandblasting them is really easy, and I think it's kind of fun too.  It's certainly more fun for me than trying to figure out how to reliably attach pictures to my posts....

Best of luck.

[grumburg]

I just took about 3 layers of paint off of mine with 400 wet sandpaper. Didn't have the guts to try anything like sanblasting. Followed with 600 and were so smooth that one coat of high-build primer made then look great and ready to spray.

[cbjunkie]

so, bob, it looks like elbow grease is the answer after all... 

[jtb]

Same as Grumburg, except I put on several coats of hi-build primer, then wet sanded out to 800.  Came out great.

[Bob Wessner]

so, bob, it looks like elbow grease is the answer after all... 

To be honest, I expected that, but I'm not forgetting the beer part either. 

[Jonesy]

I happened to thumb through a book on painting motorcycles at the local bookstore and it is the author's experience that plastic painted parts should be stripped using plastic bead blasting media. So, the sandblasting guys are on the right track. I'll be doing this with my sidecovers soon myself....

[Terry in Australia]

Sidecovers are always a vexing problem, most caustic based strippers don't know when the paint stops and the plastic starts, and doesn't really care anyway, so you end up removing not just the paint, but a goodly chunk of the sidecover too.

My Dad is an old WW2 airforce guy, and he makes plastic model 'planes, and when he needs to strip the paint off them, he uses a non-caustic oven cleaner spray, which apparently works very well, as you can imagine, the plastic in a model plane is a lot thinner than our sidecovers.

DONT use brake fluid, sure, it may well remove your paint, then it'll soak into the porous plastic and will repel any attempts to repaint it, remember, it's a hydraulic OIL. Beadblasting might be a better option, but once again, it wouldn't distinguish between paint and plastic, so be careful you don't go blowing holes in your sidecovers.

My suggestion would be to try the non-caustic oven cleaner, or even some strong paint thinner, (2 pack paint gun cleaner is great, as it just "washes" the old paint off) and if you've got access to spray painting equipment, use some 2 pack primer/filler on them, the stuff I use is actually the same color as the plastic in the sidecovers, it goes on real thick, but wet sands beautifully with 800 grit paper, makes 'em look "factory fresh", ha ha!

If anyone has any old sidecovers that they think are not worth repairing, let me know, I'm thinking of starting a changeover service for repaired, repainted sidecovers, but I need some to experiment on some first, preferably left ones, as I have a couple of right side covers (oil tank side) already. Cheers, Terry.

[Zane]

Didn't have the guts to try anything like sanblasting.

Yeah, I thought the same until I tried it on a plastic headlight pot I smashed.  I was startled by how little effect the sand blast had.  It works on the plastic I had at a fraction of the speed it worked on metal.  I guess because it's relatively soft and pliable (compared to metal) it sort of sucks up the force of the blast and gives a serious cushion effect to the process.  It's all quite easy to control and it all happens really slo-w - like whacky tabbacky  was part of the process or something.

The main thing I like about using the sandblaster (before the sand paper) is that somehow it all just comes out more even.

Easy for me to say though - since I have a kind and generous friend close by, with a big sandblasting cabinet.  So it works out kind of like our health care system - unlimited demand for a free service.....  (After I got over the shock of how little the blasting actually affected plastic, I sandblasted my tool tray and my airbox cover.  IMHO they look great with no paint at all .)

[TwoTired]

Well, since I'm not shy about controversy, I'll ask why is it necessary to strip the side covers?

I understand if the paint is peeling or has built up after ten or twenty coats.  But, I was taught that the old paint is a really good underbase, as long as it is adhering properly.  Rough sand, sealer coat primer, then filler primer for leveling (if necessary) then color, then clear coat (if required).

This is particularly good for home shop repaint over metal objects because the metal doesn't get exposed to oxidize and spoil the adhesion of the new paint.

Where have I gone wrong?

[cbjunkie]

well, i ain't sayin you wrong, exactly, but i have one sidecover with GLOPPY, CRACKED dumbass paintjob painted on it by some PO. - no way i could have told the condition before i bought it off ebay...

it will only get thicker and dumber if i paint over it...

cbj...

[Bob Wessner]

Well, since I'm not shy about controversy, I'll ask why is it necessary to strip the side covers?

I understand if the paint is peeling or has built up after ten or twenty coats.  But, I was taught that the old paint is a really good underbase, as long as it is adhering properly.  Rough sand, sealer coat primer, then filler primer for leveling (if necessary) then color, then clear coat (if required).

This is particularly good for home shop repaint over metal objects because the metal doesn't get exposed to oxidize and spoil the adhesion of the new paint.

Where have I gone wrong?

I have no experience with real painting. My side covers, based on over-spray on the rear, were originally the K0 blue/green. For some reason, the PO liked black and didn't like the original side cover badges either. Looks like he used black rattle can pain on them and you can see it was incompatible with the original paint, there are areas of wrinkling. I wasn't sure just how well primer sealers work and thought the safest approach would be get rid of it all and start over. Are you saying this shouldn't be necessary? Any additional advise is welcome.

[mrbreeze]

I had a learning experience years ago with brake fluid and plastic.I was pressure bleeding a brake system on a pickup truck. I don't know if any of you have had experience with this piece of equipment but it has a plate that attaches to the top of the master cylinder reservoir that you clamp down with chains. If you leave it too loose or get it too tight,brake fluid will go spraying everywhere when you put the pressure to it.Well, I left it too loose andgot plenty of brake fluid on my hands and arms before I got it to quit leaking.After that was under control, I went about my business bleeding each individual wheel on the truck. The next thing I know,My wrist watch went flying off of my arm.I picked up and looked at it and noticed that the little hole in the plastic casing of the watch that holds the watch band pin had disenigrated!!! Thats why I don't wear wrist watches to work anymore.

[Terry in Australia]

The trouble with the "leave the old paint on as an undercoat" theory is that if the sidecovers have been repainted like most have in the intervening 30+ years since Honda painted them first time around, unless it was you who painted them, you don't know what sort of paint was used, and you don't know what prep was done, so even if you're lucky enough not to have an immediate catastrophic paint bubbling reaction, there's no guarantee that this won't happen "down the track".

You see, there are paints, and there are paints, and they don't much like each other. You can paint enamel over acrylic or nitro cellulose laquer, or even 2 pack, but not the other way around, as the thinner in these paints will bubble enamel and turn your otherwise perfect paint to poo. It doesn't even look good from 10 feet away, like most amatuer paint jobs generally do. There are "isolators" that you can buy that will provide a shield over the existing media so that whatever you spray on it doesn't react with it, but I don't recommend this on bike stuff, because it adds another layer, and we've all seen paint so thick that the painted item loses all definition.

I painted a pair of K2 sidecovers awhile ago, but stuffed one up at the last minute, (candy paint is pretty difficult to spray properly) so I rubbed out the run, then re-applied the silver basecoat and candy color followed by 3 good coats of 2K clear, and almost filled the badge depressions! I couldn't bear to strip them and start again, so I sold them on Ebay instead, the buyer was using them on a K6, so it wasn't a problem for him as the K6 badges sit outside the depressions.

Some paints take a lot longer to react than others, and if there's a hint of silicone polish left on the surface when you paint it with anything you're in trouble again, because the paint "breathes" through pores like human skin when it is curing, and the silicon will block the pores, so the solvents in the curing paint will try to find other ways out, causing your paint thousands of tiny air bubbles that look a lot like acne.

So once again, the best way to do something is normally the hardest way too, but in the final analysis, your finish will only reflect your preparation. Paint is still relatively cheap of course, but I just hate wasting my time doing something twice, because I tried to "cut corners" first time around. Cheers, Terry.

[TwoTired]

I have no experience with real painting. My side covers, based on over-spray on the rear, were originally the K0 blue/green. For some reason, the PO liked black and didn't like the original side cover badges either. Looks like he used black rattle can pain on them and you can see it was incompatible with the original paint, there are areas of wrinkling. I wasn't sure just how well primer sealers work and thought the safest approach would be get rid of it all and start over. Are you saying this shouldn't be necessary? Any additional advise is welcome.

The rattle can stuff was probably lacquer and those solvents will attack enamels. In the late sixties and early seventies acrylic enamels were popular with the automotive industry.  I suspect that was what Honda used at the time.  Yes, lacquer solvents will attack it a cause it to wrinkle if it applied too thick and too quickly.  Both these types of paints are applied with a solvent carrier.  The surface "skins" first and this delays the release of the solvent carrier beneath it.  Acrylic enamel can take 3 months to fully cure where there are little or no solvents remaining in the surface coating.  Even though the coating is dry to the touch in a few hours.  The solvents in lacquer are quite volatile (partly why they were banned here) and active enough to begin dissolving the enamel solids before they evaporate into the air.  This leaves the surface wrinkled.  But, the base coat bond to the substrate is usually still intact and quite adhesive.

Automotive body shops do NOT strip off the old paint for a collision repair as that is too time consuming and unnecessary.  They get the surface smooth and shoot a primer/sealer compatible with their finish paint system over the old paint.  Now days, I think this is a 2 part epoxy type primer/sealer which bonds to almost any type of cured paint and provides a barrier so the finish coat and reducers can't react with the old paint.  Unless you have experimented with dissimilar brands of primer sealer and finish coat, it is wise to use types known to be compatible by the finish coat manufacturer, usually the same brand.

Much depends on what finish paint you have selected?

Also, paint layer buildup can be an issue. If surface detail is being hidden by layers of paint, stripping is the way to restore that detail.

Silicone from waxes will be an issue with any paint and the plastic of the side covers absorbs this, too.  Stripping the paint on plastic won't cure silicone contamination.  There are additives you can add to paint that minimize its effects and body shops use these routinely.  But, again the primer sealer is supposed to be an additional shield for the paint.

You will have to sand out the wrinkles and solvent flush the surface to ensure it is as clean as you can get it.

I haven't done professional painting.  But, a bit of hobbyist stuff.  I got pretty cozy with the paint suppliers and other painters for a time.  I had to stop about ten years ago when Kalifornia legislated the paints used by non-professionals out of the marketplace.  Then I lost my paint booth.  (I'm building another now.)  But, paint systems have changed significantly with the newer water based paints.  I suppose my experience could be dated.

Hope this helps,

[Bob Wessner]

TT, thanks for all the background info.

Much depends on what finish paint you have selected?

The most likely direction for paint will be one of DonD's kits. Anyone know what type of paint(s) these use and what the proper prep and sealing primer would be used with these?

[Jonesy]

Another reason for using a primer/sealer. In the DuPont paint technical manual for self-etching primer, they mention using a primer/sealer over the initial primer layer. What can happen is if you have any body filler you've sprayed over, while it was dry and covered with primer, the topcoat can penetrate through the primer and re-wet the body filler, causing it to show through the surface, even though it was perfectly smooth before you painted it. The sealer stops this from happening.

[grumburg]

Best 2 pieces of advice about painting I ever got were: 1) "Its 90% preparation, 10% application" 2) "It's not knowing where to start, it's knowing when to stop".

[swamprat]

I put the same stripper I used on my frame on an old broken side cover that was not going to be used.  The stripper only took the paint off, didn't harm the cover at all.  I tried it on the head light bucket and it ate through the paint and melted the plastic.  Had to trash the bucket.  The two must be made out of different plastics   Anyway that's my experience.  I think if I were going to try the paint stripper on a good cover I'd put a dad on the inside and see how the plastic reacts, before I covered the outside with it.