Aluminum Restoration for 1969 Honda CB750

[blake255]

Hi,

This is my first post, so let me introduce myself. I'm Blake from Georgia. I've been lurking, reading, and experimenting for a little while now. Thanks to all you guys who have been so generous with your experiences and opinions, and to Caswell for hosting the forum.

I've had some success with basic aluminum polishing, so now I want to get down to business. I'm restoring a 1969 Honda CB750 and I want to get the aluminum engine covers as close to factory spec as possible. At that time Honda was producing more bikes in a month than most manufactures were producing in a year. So a very basic satin / brushed finished was used. The finishers didn't even knock off all the casting marks or bother to get in the crevices or bolt recesses. They just hit the visible areas with some type of abrasive tool and then clear coated the piece. But they were working with a freshly cast part, so the finish was nice none the less. Below is a picture of a perfect example of a CB750 rear wheel. You can see the brushed finish marks running in different directions on different areas and the "bumpy" rough cast areas as well. Even though it was a quick process, the piece came out nice and bright. Fast forward to today, I want to achieve the same finish, but I now have to deal with 40 years of oxidation and corrosion in every nook and cranny. I know it can be done because I’ve seen other very nicely restored bikes. The key is to not “over restore”. My main goals are to do it right and to do it myself. If any of you pros out there would share how you would approach this project if it were brought to your shop, I would greatly appreciate it.

Tools that I have readily available are:
1 hp, 1800 rpm buffer w/pedestal
Expander wheel with 3M Trizact belts of various grits
Sisal, Spiral Sewn, and Loose buffs, 10" & 12"
Emory, Tripoli, and White compounds
Large ultrasonic cleaner w/ Bransonic buffing compound removal solution
¼” die grinder

I’m open to buying new tools or supplies to do the job right, so let the suggestions fly.

[woodjames]

That's really close to what 400 grit greasless compound will give you. Another plus of using that is that there's no cleaning necessary afterwards. Ohh yeah forgot - Welcome to the group!

-Jimmy.

[baz]

yes i agree , it looks close to 400 greaseless
you could also get similar results with scotch brite belts, the blue or black belts if available in the sizes for your expander wheel
if the parts are in bad shape i would sand down the part with coarser grit abrasives first then glass bead the the whole part to get a clean blasted profile in the areas that you don t want the brushed finish then go over the part with greaseless or scotchbrite belt , clean with hot water ans soap
dry final clean with alcool or acetone then clear coat

[blake255]

I knew you guys would have some good ideas. I like the idea of a 400 greasless if paired up with a loose wheel. The valve cover has a lot of contures compared to the hub. I was also considering experimenting with a scotch bright wheel, so I will probably go ahead and do that now. I was glad to see that Baz addressed glass beading because it was actually the first thing I thought of to bring the part back to a "base" finish. I used an 80 grit glass bead and thought that the finish looked a little rough. Maybe it was too much preasure, or maybe I should use a finer grit. I also experimented with Armex coarse blasting soda as well, but not really happy with that either. Of course, the blasted texture may even out when I clear it with VHT. What do you think? Thanks Jimmy, Baz

Blake

[XK120DHC]

I'm restoring a 1969 Honda CB750

Blake;
Wow! a 1969 Honda CB-750-4.. I worked on these bikes when new! (worked at a Honda/Bultaco Dealership back then.. I had a '50 Harley "EL" V-Twin )
Well, you made me feel VERY old!
Best of luck with your restoration.

[blake255]

Charles,

Thanks for the post. You should head over to forums.sohc4.com. There are a few thousand of us Honda inline four nuts over there. You may just catch the fever again.

Baz,

You’re a genius. I was casually re-reading your post when it struck me that I didn't catch what you were actually telling me.

sand down the part with coarser grit abrasives first then glass bead

The first thing I did when I started this project was grab some old parts and bead blast them. I was surprised how they maintained that old dull and stained tone. I was expecting something much brighter. That's why I wrote that I wasn't very happy with it in my last post. I guess a more experienced guy would have known this. But on re-reading your advice, I went to the garage, grabbed a part and sanded it on the expander wheel leaving an area of each grit level exposed. Then I glass beaded it. It had that bright and even tone I was after. Now I see that the glass beading didn't remove enough of the oxidized metal.

So now the eternal question, cartridge rolls or felt bobs with glue & grit kit to get into the recesses with my die grinder?

Blake

[XK120DHC]

Charles,

Thanks for the post. You should head over to forums.sohc4.com. There are a few thousand of us Honda inline four nuts over there. You may just catch the fever again.

Blake

Blake;
I'm afraid that "catching the fever" is WAY out of the question..
I raced motorcycles for ten years, three as an AMA "Class C" Pro (Flat-Track, RoadRacing, TT Scrambles, etc.) and have the broken bones (including a Conpacted C-4 & Fractured C-5 acquired June 13, 1973), arthritis, etc. to prove it.
I still have my Z-50 Mini-Trail "Pit Bike", have acquired all the parts necessary to rebuild the engine, new tires, etc. and THAT will be the extent on my two-wheeling at this stage in my life.
But thanks for the "offer"

[baz]

Charles,

Thanks for the post. You should head over to forums.sohc4.com. There are a few thousand of us Honda inline four nuts over there. You may just catch the fever again.

Baz,

You’re a genius. I was casually re-reading your post when it struck me that I didn't catch what you were actually telling me.



The first thing I did when I started this project was grab some old parts and bead blast them. I was surprised how they maintained that old dull and stained tone. I was expecting something much brighter. That's why I wrote that I wasn't very happy with it in my last post. I guess a more experienced guy would have known this. But on re-reading your advice, I went to the garage, grabbed a part and sanded it on the expander wheel leaving an area of each grit level exposed. Then I glass beaded it. It had that bright and even tone I was after. Now I see that the glass beading didn't remove enough of the oxidized metal.

So now the eternal question, cartridge rolls or felt bobs with glue & grit kit to get into the recesses with my die grinder?

Blake

glad i could help but hey i m no genius , it is just that i have been there before you .
for the eternal question , i prefer cartridge roll , i never really had good success with feltbobs .

[woodjames]

Ditto that. I've got a gallon of 320 grit adhesive compound, I use it once in a while on q-tips for really tight radii. Maybe it's just me but the most part it just makes a cloud of dust when I use it. In addition to cartridge rolls, dremel sized sanding drums can be found in a huge variety of grits through lapidary suppliers.
I keep a can of wd-40 on hand while sanding, seems to help it "cut" rather than just smear the aluminum, and the paper lasts longer.

-Jimmy.

glad i could help but hey i m no genius , it is just that i have been there before you .
for the eternal question , i prefer cartridge roll , i never really had good success with feltbobs .

[baz]

Ditto that. I've got a gallon of 320 grit adhesive compound, I use it once in a while on q-tips for really tight radii. Maybe it's just me but the most part it just makes a cloud of dust when I use it. In addition to cartridge rolls, dremel sized sanding drums can be found in a huge variety of grits through lapidary suppliers.
I keep a can of wd-40 on hand while sanding, seems to help it "cut" rather than just smear the aluminum, and the paper lasts longer.

-Jimmy.

never tried with the wd40 , something new to try this week . i have a set of old shovel hd heads to do complete so plenty of areas to try new stuff
thanks