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The Case for Banning Rubberized Undercoating
For the third weekend in a row I walked into the garage, looked at the frame of my Honda XR600R, then down at the floor. I checked the freezer for something that was never there and bee-lined back out the door and into the house.
To say I’ve been avoiding the project—stripping and painting the bike frame—is an understatement. I’ve been avoiding it so much that I’m scared to look directly at a pile of steel tubing. This week, our metaphorical eyes finally met, and it was not the Hollywood meet-cute I wanted it to be. It was exactly what I expected: A smelly, time-consuming mess.
The frame of my 1988 Honda bears all the signs of a life full of tales and adventures—everything a big-bore dual sport could dream of, followed by torture at the hands of a mechanic who could have inspired the Saw movie franchise. The last and worst task for me to complete is to strip off the rubberized undercoating that was hastily applied to every nook and cranny of the steel frame. I knew this job was going to suck from day one, when I handed the guy $800.
You haven’t tried to remove this stuff before? I’m jealous. I’m not an expert on the process or product, which is likely why I despise it. Rubberized undercoating in an aerosol can possesses magical powers that turns anyone capable of holding a spray can into a chaos machine. This is the most annoying-to-remove coating this side of the plaque on my front incisors—judging by how the hygienist scrapes at my teeth every six months.
Undercoating is cheap, available at most hardware stores, and is pretty dang durable. When used properly, rubberized undercoating can solve more than a few problems while all but ensuring that someone down the road will be forced to deal with different problems that are even more annoying. The previous owner of this motorcycle wanted to paint the frame black while hiding some surface rust and poor frame repairs. Rubberized undercoating did all of that … and more.
It plugged all the small drain holes in the bottom of the frame that are meant to keep moisture from building up and prevent rust from forming. When the bike is fully assembled, these holes are located in areas easily accessed by a spray can, and overspray on many other parts suggests that is exactly how this machine was painted. Anything that could be directly sprayed got a solid third coating, likely right after the words, “Well, since there is still some in the can left, might as well.”
My usual go-to for stripping frames—a sand blast cabinet—would be a giant waste of time. The thick, soft undercoating effectively catches the grit as it shoots out of the nozzle with 85psi air behind it. After trying a few different techniques, and cleaning a mere fraction of the frame, I gave up. Now I had a frame that still needed to be stripped, and blasting media contaminated with rubber chunks. What’s more fun than changing out the blast media in a blast cabinet?
Realizing there likely are and never have been any shortcuts, I called upon my trustiest tools: A Motion Pro gasket scraper with a bright blue handle, and an old favorite: A corded drill. Rarely do I need it but, with a wire brush in the chuck and the likely-illegal-now adjustable trigger lock, which makes holding a steady rpm a breeze, I knew I could run this drill can run all day and it wouldn’t complaint.
The undercoating was so thick that it laughed at my drill and its spinning wire wheel. Instead of being ripped off the frame, the black schmoo built up heat and started to smoke, leaving a low cloud of burnt rubber sitting in the garage. I realized the scraper was my final hope.
It worked beautifully… sort of. As I scraped, it became clear that beneath the undercoating was a layer of black spray paint and then, finally, the factory-applied Shasta White, some of which still had shine where the can-wielding dingbats didn’t bother to sand or prepare the surface. The scraper peeled back all the layers pretty effectively in more open areas, but places with more complex contours, like the multiple tabs and mounts for the rear suspension linkages, proved thoroughly annoying. About then, a friend told me to try aircraft stripper.
I would have tried anything. The can of aircraft stripper bore a warning label about using in a well ventilated area, and I take those instructions seriously. Thankfully, spring is trying to happen in my driveway, so I could work either in the garage with the door open or in the driveway. Applying coat after coat with a chip brush, to keep the gel wet, took hours. As I brushed, and brushed some more, the black finish lifted, then wrinkled. Finally, it loosened enough to be easily removed with a pressure washer. Just applying the stuff—not washing it off—took most of an afternoon. To get a level of clean I will be satisfied with will require a second application, then more clean-up. All to undo the mess made by someone who likely just grabbed whatever was on their workbench, shook the can, and went to town.
Spray paint I can deal with. This rubberized undercoating? You should need a special license to buy a can. At the very least, people need to understand this is not some powerful elixir that turns a frame from rusty into showroom fresh. It merely hides a mess and often makes whatever you’re trying to hide even worse. Covering rust with undercoating traps moisture and allows the rot to get worse—you just won’t see it. Who is that really helping?
Oh well—someone has to create restoration projects for us to work on. If the main flaw of your project isn’t rubberized undercoating or rust, it’s another … or, in this case, both.
That does look like a royal sticky mess to get off. Playing with power washers is fun though!
One thing we have to remember with our toys is that the previous owners did what they did within their skillset to keep them going so they could enjoy them. When they couldn’t do that anymore, they sold them to us. We are the ones who accepted the challenge.
I try not to bitch much about something I find that someone else did. I’m old enough to know that someone somewhere is swearing over something they’ve found that I did!
The immortal words spoken by every bodge job to get a hot mess of a project sold: “Looks good from my house!”
I’ll confess that I’ve used the ‘ol rattle can Rocker Panel Reformer on some rigs in an attempt to squeeze another year or two of life out of them.
I think that using a Heat Gun to soften it would make scraping it off easier.
Or maybe just light it on fire?
Softening it seems to make it more difficult to scrape, but I just might have to try a heat gun.
I appreciate your posts, Kyle, and how you weave your thinking into your project descriptions. One thing, though, how about captions for each of your pics? That would be super helpful! Thanks for your writing and pics!
Sorry, didn’t realize i was replying to a comment! Hard to do and see stuff on a phone screen!
That thing needs to be dipped. Not so easy in your garage and driveway of course, but I saw them dipping entire car bodies and it was amazing. Pretty big tank and you probably could have slipped your XR frame in there (unnoticed).
But I’ll bet that your way was a lot more fun, so… good for you!
Was thinking “dip it” whole time reading the article.
Mustang forum I was reading swears by oven cleaner and some tool called a “crud thug” –but I haven’t tried either.
Have seen the hot torch and scraper method… pretty nasty.
The best way to restore your frame is to sandblast it then powder coat it. I can do it for if you wish. I have a big sand blaster outfit and a big oven. A little 5hp compressor isn’t going to do the job.
I detest powder coating. Any imperfection or chip in the surface and rust will follow as powder coated will hold the moisture. Ford had oil pans rust out due to powder coating. I had a trailer I bought new, only to have the frame rust out due to powder coating. I thought it would be the last trailer I would own. When I replaced the trailer, I made certain it was painted, not powder coated.
I don’t like to powdercoat my frames based on the logic that most of my frames are steel and flex, potentially cracking. I’ve seen powdercoating be thick and durable enough that it can hide a crack in the frame underneath. With painted frames I can see the damage, repair, and patch the finish if I needed to. I’ve found paint durable enough for my needs. Of course, everyone’s projects and needs are different.
I cleaned a really crusty set of cylinder heads ( cast iron),
sludge,rust and deposits in coolant passages and they turned out beautiful!
They are ready for a ‘check and deck’.
I got some muriatic acid and soaked them down.
(DISCLAIMER!!)
(wear rubber gloves and do it outside!)
Awesome results!
Let soak for 20 minutes, reapply twice,then pressure wash
They look brand new
Also wear a chemical respirator and serious eye protection.
Anyone else done this?
Acid bath would have been the shortcut, but you’d need a lot of prep room
OK, gotta ask. The black banner on the wall. What crankcase is that?
It is marked as a Cadillac V-16 but when I talked about it in another article (https://www.hagerty.com/media/automobilia/our-two-cents-7-of-our-favorite-pieces-of-automobilia/) the accuracy was called into question. Still interesting to look at!
Interesting. Never saw that one before.
XR frame doesn’t look too bad. Looks like a couple of repairs, but at least the subframe isn’t broken off. Beast of a bike. My daily driver has been a 650 for years.
Steam Jenny. Will remove most anything. They were a must-have for doing heavy equipment engine rebuilds. Expect to wear a bunch of the crud you’re blasting off.
Some things you just take to the dry ice blasting guy and stop worrying about it.
It comes right off with heat , a propane torch would have been your friend doing this job instead of all the whining, you could have wiped it off with a rag
Did you try the same stuff we use to remove powder coat? Aerospace paint stripper? Not sure if that would work or not. Put down tons of news paper and paint the gel on and let it work. Powder coat generally falls right off not sure if rubberized coating would too?
I used to build SuperKarts from scratch. We found that sand blasting the chassis changed the way it performed on the track (the chassis is the suspension). The process of powder coating and sitting in the oven didn’t negatively affect it but the sand blasting did. After that I have never sand blasted any frame. Quad, bike or kart.
Interesting insight re: the kart chassis bits. The stripper I used was the standard aircraft stripper, yes. This being my first time using it I likely could have done less. Probably should have let it sit and work longer. Learned that for next time.