Topic: Any Advice on Polishing Engine?

[campbmic]

I have my engine out of the frame for a restoration and was hoping to get some advice on how I could polish the engine/covers to try and get it close to this example;

https://www.cycletrader.com/listing/1971-Honda-CB-350-5008670005

If you look at the outside pictures you can really see how great the engine looks. I've heard of "wet medium blasting" and Im pretty sure that's too expensive for me. I understand that regular "medium blasting" can be some what affordable. What medium should I search for? I've heard of using sand, baking soda, nut shells, etc.

What I'd really like to figure out is if there's any DIY garage way of doing it. I understand the basics of going from low grit to high grit, but am lost after that. I don't really understand when to start using steel wool, polishing compounds, etc. Or what the different polishing compounds do. I know there are hundreds of different wheels/brushes/compounds, if anyone has advice on what sandpaper grits to use and the next steps I'd greatly appreciate it!

[jaytee-nz]

There's a lot of information out there on this subject - try this for a start http://forums.sohc4.net/index.php/topic,97153.0.html

[campbmic]

Thanks Jay! I tried using the search but just found a bunch of people mentioning "polished". I'm going to follow "Monos" recommendation

I did not want a mirror finish, but close to mirror, and got great results in 4 steps:

1. wet sand with good quality 600-grit paper to remove the factory clearcoat and sand out any dark oxidation spots.  i say "good quality" because i bought a pack of wet/dry paper from harbor freight and it left a gray residue, making the aluminum look dirty.  also, the grit quality was pretty uneven.  i ended up using some 3M sandpaper and it worked so much better.  ya get what you pay for i guess!
2. (this is actually counter-intuitive) - i used a 4" 400-grit 3M radial bristle wheel (blue) that i have mounted to my polishing motor to give everything a satin finish.  the 3M radial bristle wheels are actually very non-aggressive, and the 400-grit left a nice smooth satin finish - comparable to 800-grit.
3. buff with a 6" stitched cotton wheel and tripoli.
4. final hand-polish with Blue Magic and a microfiber cloth.

I'll be posting images of this process if i can ever locate my build thread.

[RAFster122s]

Mark what compound you use on a buff wheel and do NOT mix with other compounds. It is the only way to step through different compounds without the previous compound continuing to cut. The pressure you apply and direction of polishing is a little different when doing the final coloring steps. The Caswell's guide is excellent.

If you do not have any nicks to sand out you can try a part sanding with 600 but you often are better served by sanding with 320 or 400, 600, and then 800 if you want it to have a very high polish.

Polished aluminum is addictive.  It is often glossier than chrome.

David


PS. Wear a good dust mask as polishing is very very bad for your lungs. Very important!!!

[pjlogue]

I have used the 3M wheels on a bench grinder.  Medium for heavily weathered engine covers then go to fine.  I then clean everything and use a buffing wheel.  This gives me a soft shine.  I then use warm acetone to clean off the wax from the buffing compound.  To protect the covers I then use Diamond coat clear. 

You need to remove any lacquer before you start the refinishing.  You can buff the piece to the amount of shine you want.  I have used dremmel's to get into tight spots.  The Diamond coat clear has held up well, does not dull out the bare metal look of the aluminum nor does it yellow with heat/time.  It is also impervious to most solvents.

I have had problems with areas of smut on alloy aluminum that has weathered.  The 3M wheels will remove a lot of it but heavily weathered covers are tough to get the smut out of.  The smut is from the Copper in the alloy.  I guess there must be a way to chemically convert the oxidized copper without harming the aluminum but I haven't tried this.
-P.

[Don R]

 You may be tempted to use a coarser grit. Don't do it, the scratches it makes will double the work.

[Doobie]

I start with 400 wet and work up to 2000, then buff with either grey, brown, white, green compounds depending on the end result I'm going for. I like to get high on aluminum dust particles (not really, I use a respirator but I'm addicted to polishing).

[campbmic]

Mark what compound you use on a buff wheel and do NOT mix with other compounds. It is the only way to step through different compounds without the previous compound continuing to cut. The pressure you apply and direction of polishing is a little different when doing the final coloring steps. The Caswell's guide is excellent.

If you do not have any nicks to sand out you can try a part sanding with 600 but you often are better served by sanding with 320 or 400, 600, and then 800 if you want it to have a very high polish.

Polished aluminum is addictive.  It is often glossier than chrome.

David


PS. Wear a good dust mask as polishing is very very bad for your lungs. Very important!!!

Raff I think I found the guide you were talking about here;
https://www.caswellplating.com/buffman.htm

Thank you for the suggestion! That is exactly what I was looking for!
1. Are the engine cases/stator cover/points cover/carbs all made from aluminum?
2. About half way down the caswell guide is a chart. I'm assuming the "X" means use this compound with this Buff type, is that right?
3. I havent decided if Im going to use the 3m wheels or the high grit wet sand for the first step. For the second step do I follow the Caswell chart by doing A, B, C to get the best result. Or do I just do one of them?
IE if I want the best results do I "wetsand/3m wheel then C" or "wetsand/3mwheel then A then B then C"?

Thanks again for the guide! That should be a sticky somewhere!

[RAFster122s]

Yes, the compounds used for aluminum is most commonly started with brown/tripoli and then you progress to white to buff to a high polish and some go beyond white to blue to color the aluminum.

The different types of buffs used are shown in Caswell's guide along with the compound to use with that buff.

The sanding is needed to remove any imperfections and oxidation build up.  The stock cast aluminum used by Honda and others back in the 60s and 70s was not always pure and the copper and other contaminants can sometimes make polishing a challenge.

some guys polishing will just hit it with 400 grit and then move to buffing but you will not get the same results as when you sand the part progressively finer to at least 800-1000.
It is easier to start over when you have not gone too coarse on your sanding.  You want all scratches left from the sandpaper to disappear  by the finer grits to the point you do not see any scratches before you start buffing.  The sanding is dirty and hard work taking its toil on the fingers and hands but it is worth the end results when you finish buffing.

Items you are buffing can and usually will get pulled out of your hands at some point so, keep this in mind. Having foam mats down on the floor and behind your buffer can lessen damage to the parts when they go flying...  The black buffing dust gets Everywhere, so keep this in mind when you set up your buffing area.

[754]

Points cover is usually steel. So is the 750 clutch cover..

[campbmic]

One last question, after the final stage of polish do I just wash the polish off?

Is there anything I need to do like clear coat it or anything?

Thanks for all the help! Once I have everything setup Im going to take pictures and document the process.

[pjlogue]

For easy to reach spots you can use aluminum polish from time to time.  Water (after rain or washing) will leave marks though.  I use Diamond Coat clear to cover all the aluminum parts I have spent a lot of time restoring.  It is the only thing I have tried that doesn't 1) yellow with age and 2) does not "dull" the look of fresh aluminum.  Any of the clear coats, clear powder coats, lacquers have all taken the bare aluminum look away. 

If you go with just polishing, wipe away the excess and leave it.  The wax in the polish leaves a protective layer. 

-P.

[Doobie]

One last question, after the final stage of polish do I just wash the polish off?
Is there anything I need to do like clear coat it or anything?

No need to clearcoat. Any good metal polish will keep the aluminum shiny for a long time. FYI, there are also numerous YouTube vids on polishing techniques.

[campbmic]

So I bought this today and Im having amazing results so far! The engine parts are coming out like chrome. Im going to take a few pictures and do a small write up in the next day or two.
https://www.harborfreight.com/14-piece-aluminum-polishing-kit-98707.html