Tech Tip: Aluminum Polishing 101 w/ Herm from Dime City Cycles

Ok, so your engine covers are in desperate need of attention. First, you think paint, but having a full winter to work on the project you commit to polishing them. Now the question is “What do you need and how is it done?” Here’s a quick way to get those cases to bling!

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First, get yourself an intern! Then get a good bench buffer. The 6” models from places like Home Depot or Lowes are ok, but will take you twice as long to get the result you want. Try to get at least an 8” 3/4HP 8amp unit (1hp is the real deal).  You’ll thank us later. A bench grinder motor will work fine too. There are a ton of sites on how to set up your own polishing motor from used dryers, washers, etc. Whatever you use, make sure it is no less than 3400 rpm.  Anything less isn’t possible for polishing.

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Next, get some wheels and buffing compounds. We use a sisal wheel, spiral sewn, and a canton flannel wheel along with some emery compound, Tripoli compound, and white rouge. For final finishing I like the Autosol polish as well. All supplies can be ordered from They have a real good supply of buffing and polishing gear. Your local hardware store will have some too. You’ll also need some good wet/dry sandpaper, I like to have all grits on hand, from 220 up to about 1000. And lastly, get a can of aircraft stripper and some rubber gloves. This can be found at any automotive parts store.

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For this scenario, we’ll use an engine case that’s in really bad shape. The cover has a deep gauge in it, and as you look closer the finish also has a coat of that old yellowed clearcoat on it, and to top it off, the aluminum is badly oxidized from sitting for the last 30 years.

First thing we need to do is remove the clearcoat with the stripper. Put your gloves on and be careful with this stuff, it will chemically burn your skin instantaneously.  Trust me, I know! First, scrub the part with some very fine steel wool to break the surface, it allows the stripper to sink in under the clearcoat better. Spray the part thoroughly and let sit.  You’ll see the clearcoat start bubbling almost right away. After about five minutes just brush it off with the steel wool and wash the part real clean.

Now the sanding begins. If it weren’t for that deep gauge you could go right into the cutting, but we need to try and get rid of it first. Start with some 400 grit. Wet sand until it’s gone. If the rest of the part is ok, you can move to 600, then 800 throughout the entire part. This could take some time and will be messy, so have at least a six pack nearby! (Depending on how deep the gauge is you may have to start with lower than 400 grit.)

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Now we’re almost ready for the fun to begin on the buffer.  But before you start here’s a few setup tips;

Wrap a towel around the base of the buffing motor, maybe duct tape it down so it doesn’t get caught up in the wheels. Also put an old blanket on the floor and on the bench. Believe us here: The buffer will at some point grab the part and cause it to FLY OUT OF YOUR HAND.  It will happen!

Use cotton gloves.  The oils from your fingers will drastically alter the compounds effectiveness. I have a few different sets of gloves, one for each wheel. Nothing sucks worse than having to go back and forth to take out emery scratches… well, parts flying out of your hands sucks pretty bad too.

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Use only one compound per wheel.  NEVER, EVER, mix them. Use a sharpie and label your wheels.

If your part gets too hot, let it cool. A cool part polishes much better and the compound won’t cake up. Alternate your parts while letting each one cool by a fan.

Put compound on the wheel often. How do you know if there’s enough on? When you feel dusty-like bits touch your face and you can’t help but wipe, then it’s enough. Make sure you’re wearing safety glasses, of course.

And, MOST IMPORTANTLY, aluminum oxide is a direct cause of Alzheimer’s disease so wear a mask or wet bandanna always when sanding it or polishing!

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Ok, now we’re ready, let’s get to work!

First step, use the black or ’emery’ compound and that new ‘sisal’ wheel. This process will remove any leftover oxidation as well as the small scratches left by the sandpaper. The compound will ‘cut’, but don’t expect it to do a lot real fast. Take your time here and DO NOT push the part against the wheel very hard. Get a feel for it and be careful not to feed any irregular angles into the wheel or it will launch! Keep cutting until you have even color and all scratches are gone. Don’t expect or try for a mirror finish just yet. Also remember to let the part cool down from time to time.

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[Hey Herm, where’s that mask?] – [Huh, what mask? Who’s Herm?]

Now the blingin’ begins! Move to the Tripoli compound and a ‘spiral sewn’ wheel. But first, clean your part. The best way is to wipe it with a clean cotton rag and some all-purpose flour. The flour soaks up oil microscopically, and doesn’t scratch the surface. Again do not push hard into the wheel and take your time. Sometimes if the oxidation is not too bad, and if we sanded up to 1500 grit we can start with Tripoli instead of emery. But if there’s oxidation emery is a must.

Tripoli finishes are pretty good for most people including the crew here at DCC. We like it because it gives us the vintage feel and look we like for most of our bikes and it’s real easy to maintain. But if you want a real mirror finish move onto the white rouge.

This final step is where your part will emerge with some serious professional looking results. This part is called ‘coloring’, as opposed to buffing. You’ll need the white rouge compound and the canton wheel. Again, clean your part with a cotton rag and flour before starting. With rouge, you need very light pressure on the part, and don’t let the part get hot! It’ll change the color of finish and not get you the results you want.

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In some cases you might need to break out the Dremel to get into the tiny areas that can’t be reached with the buffing wheel. Use the same steps with the small buffing wheels on the Dremel which can be had from any local Home Depot or Lowes.

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Your part should have a mirror finish now. If you’re happy with it, once the part is completely cooled, use the Autosol. The Autosol will basically give the part a final cleaning and leaves a protective film to help prevent future tarnish and makes it easy to clean and buff while on the bike every now and again.

dime city cycles,cafe racer,aluminum polish,polishing,honda,tech

dime city cycles,cafe racer,aluminum polish,polishing,honda,tech

dime city cycles,cafe racer,aluminum polish,polishing,honda,tech

– Herm Narciso

9 replies
  1. Todd
    Todd says:

    Excellent write up, Herm. I’ve been reading up on polishing a lot for my rebuild, and so many people gloss over a lot of the details, such as minimum RPMs for the buffing wheel, not to mix compounds on one wheel, etc.

    Thanks for being so thorough and sharing.

  2. Todd Ethridge
    Todd Ethridge says:

    Excellent explanation of a process that is both easy and difficult all at the same time. I like the warning that you will “launch parts” and that brings up an important point. If you are polishing an irreplaceable part, you need to be extra careful and perhaps go for hand polishing and less than perfect surface, rather than risk losing an expensive part. I once lauched a cam cover for a Moto Parilla across the room and watched it shatter into about seven pieces. Took two years to find another. I didn’t polish the second one…
    Also, I learned the hard way about mixing compounds, don’t…

  3. Thom
    Thom says:

    Wow. Seriously, just wow. No one has ever taken the time to explain all this to me, and I’ve been doing it wrong for years. You’ve just saved me tons of work on my next project. Thanks!

  4. scott
    scott says:

    I have a 1974 Norton commando that I got from a friends dad after my friend died. He never got to ride it and I had no idea what to do with it till I watched this show. I hope one day I will have the money to fix it. Till that day I will live through this show.

  5. Andy Kanani
    Andy Kanani says:

    A great,well written article. I was considering saving/salvaging my car’s wheels from bad curb rash/deep scratches but i think i will bite the bullet and get new ones on line forabout $500. Trying to save money but with the time and money & effort to repair I am doubting it is worth it? As a non-mechanically incline guy, this was very informative. Thanks Andy.

  6. Tristan Scarfo
    Tristan Scarfo says:

    Thanks for the tips…just finishing polish on crank cases and some covers…any advice on clearcoating? Products? Necessity?
    Thanks again,

  7. Bruce Cook
    Bruce Cook says:

    Hey Herm!
    Interesting and very informative. I just spent about twenty hours cleaning internals on my /80 Honda 750F carburetor. After 17 years in storage the bike looked great on the outside…not so with insides of those four carbs. Now just polishing the top caps, and your video is going to save me wasting MORE time. The Home Hardware paint remover didn’t work…but probably roughing up the surface beforehand is all I need to do, eh? Thanks!


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