- Product Mentions
- Other References
- Refinishing Rough Cast Aluminum
- Refinishing Bing Carburetors
- Refinishing Chrome Headers
- Refinishing Faded Black Plastic
I’ve had several questions and Email about how I refinish the rough aluminum casting on the engine, transmission and rear drive and also some questions on how I got the carburetors to look shiny and new again.
NOTE: Refinishing is not rebuilding. Refinishing is restoring the surface of parts to “like new” condition. You are removing crud, stains, grime, dirt, grease, bugs, corrosion, tar, mud and old gasket sealer that have frequently been baked on for 10, 20, 30 or more years. It takes PATIENCE. It is applied Zen 🙂
I make reference to specific products not to say these are the ONLY products that can work, but to be clear about what products I have used. YMMV. In particular, I have used AutoSol metal cleaning products and keep several of them handy. Here are links to the manufactures sites for you reference.
- Metal Polish, Liquid
- Aluminum Cleaner, Spray Liquid
- Aluminum Polish, Paste
- Aluminum Protective Oil, Spray
- Bluing Remover For Headers
Hardware Store (Ace, Home Depot, Lowes, etc.)
- Scotch Brite Pads
- 600, 1500, 2000 Grit wet/dry paper
- Steel Wool, “00”, “000”, “0000”
- Nylon brushes
Auto Parts Store (Napa, AutoZone, O’Reilly’s, etc.)
- Brake Cleaner
- ChemTool B-12 Carburetor Cleaner
- Engine Degreaser
- Parts Cleaner Solution – NAPA: Aqueous Solution
Here are some references I’ve found that have advice, information about cleaning methods, product lists and ideas about refinishing techniques.
- Bob Fleischer, Maintaining the Paintwork and Aluminum
- Mark Holbrook, Cleaning Aluminum Engine Components
- WebBikeWorld, Motorcycle Metal Polishing Reviews and Information
Refinishing Rough Cast Aluminum
There is a lot of cast aluminum in the R75/5: engine, air box halves, intake top cover, front cam cover, transmission, rear drive, lower fork tubes, front brake plate, and wheel hubs. Here is what I started with.
I start with engine cleaner to remove as much of the baked on grease and grime as I can. I use several kinds of nylon brushes, Scotch Brite pads and tooth brushes to get the junk off. I used engine cleaner on the entire bike before I brought it into the shop. I also used it to clean out the inside of the bell housing around the clutch and the exterior of the engine. I use a spay bottle of water to wash off the cleaner onto a thick layer of newspaper on the shop mat to soak up as much of it as I can.
Brake Cleaner and Parts Washer
After I got the gunk off with engine cleaner, I put the smaller parts that fit into my parts washer and use the nylon brush and tooth brushes to get any remaining crud off. I use brake cleaner on stubborn stains and baked on tar. I also used it on exterior of the engine.
Scotch Brite and AutoSol Aluminum Cleaner
For the rougher castings found on the engine and transmission, I use Scotch Brite with the Autosol Aluminum cleaner. This usually removes stains from leaking battery acid, gear lube and oil.
This comes in a variety of roughness. I use “00” rougher up to “0000” very fine. I use this with the Aluminum Cleaner to really renew the the pores in the cast aluminum. It quickly brings back a sparkle.
Wet/Dry Sand Paper 600 – 2000 Grit For Scratch Removal
Some parts that were polished had scratches in them. For example, the shock covers. I used wet/dry sand paper starting with 600, then 1500 and finally 2000 grit to remove the scratches. Then I polished them with Griot’s polish starting with Polish #1 and ending with Polish #3. Then I finished up with Aluminum Polish.
Metal Polish, Aluminum Paste Polish, Aluminum Protective Oil
The last step is to polish the aluminum. For rougher parts, i use the AutoSol Metal Polish. For polished aluminum or fine grained castings, I use Autosol Aluminum Paste polish. I apply this with blue shop towels and remove the blackened residue with a clean section of the towel. I finish up using a microfiber towel. Finally, I spray the part with AutoSol Aluminum Protective Spray and let it sit for about 30 seconds and then lightly buff it with a clean microfiber towel.
Here’s the results.
Refinishing Bing Carburetors
To be clear, this covers cleaning and polishing the EXTERIOR of the carburetor body. I do NOT use abrasives, steel wool, etc. on the internal parts of the carburetor, only the exterior of the carburetor body.
Soak in Parts Cleaner Solution Overnight
I started with this (on the left) and ended up with this (on the right) after soaking the entire carburetor in parts cleaner overnight.
Then, I use a tooth brush and my parts washer to remove any remaining dirt and crud off the outside of the carburetor.
Disassembly and Soak in Carburetor Cleaner
I use Chemtool B-12 carburetor cleaner. WARNING: This is very nasty stuff. It eats nitrile gloves. Use rubber kitchen gloves when handling it and keep it off your skin. Wear safety glasses when working with it.
I disassemble the carburetor and soak all the parts overnight in bins.
This is what the body looks like after I use a tooth brush with Chemtool B-12 to clean any remaining varnish and crud out of the creases and crevices of the carburetor body.
Polishing Exterior of Carburetor Body
Here are the basic tools I use AFTER I have soaked the carburetors in Chemtool B-12 carburetor cleaner overnight followed up with a tooth brush scrub with B-12.
Most of the work is done with “0000” steel wool and AutoSol Aluminum Cleaner. I spray the AutoSol cleaner and then use the steel wool to return a shine to the aluminum. In the hard to reach places. I use the the brass wire brush and brass Dremel tool to get into some of the curved and hard to reach creases in the body. I use a lot of blue shop towels to clean the blackened residue off as I go. Next, I use the AutoSol Metal Polish and a blue shop towel to bring the luster back to the aluminum. In hard to reach places, I put a brittle brush on the Dremel tool to polish. Again, I use a separate blue shop towel to buff and remove the black residue. I sometimes use the AutoSol Aluminum Paste polish. It works well on already polished surfaces but I find the liquid Metal Polish works better on the rougher cast aluminum found in the carburetor body. I polish up all the exterior metal hardware (linkages, levers, nuts, etc.) using the Metal Polish and-you guesed it-more blue shop towels. Here is the final result after several hours of applied elbow grease.
Refinishing Chrome Headers
I have used AutoSol Bluing Remover and Semichrome paste with good results. You can read about the work I did to refinish the header pipes here:
And here is the Before and After pictures.
Refinishing Faded Black Plastic
I got a comment from a reader that I should try “Forever Black” on faded black plastic to restore the sheen. I tried that on the handlebar switches and I think this is going to be my new “go to” for plastic restoration.
Pingback: 1975 R75/5 Rebuild: Some Refinishing Information | Motorcycles & Other Musings
Thanks for the amazing break down of everything. Quick question. I just received an r75/6 motor without the cylinders on it. The engine block is caked with crud but the inside is surprisingly clean. How can I safely clean the outside without damaging the inside? And also, if any materials/liquid I.e. Water – chemicals get inside engine how would one clean that out? Thanks!
Thanks for stopping by and I’m pleased this material is helpful to you on your project.
If the cylinder studs are with the block, I’d cut a piece of 1/4 inch plywood to fit over the opening for the pistons and then tape the edges with masking tape. You can clean the block using engine cleaner and brushes, and clean with aluminum cleaner as I describe. I used a spray bottle to wash the engine cleaner off the engine so water didn’t get inside the engine.
If you are concerned there is debris inside the block where the crankshaft and rods are, you can you use brake cleaner to clean that out. If the oil pan is removed, any crud inside will drain out. Then, I would use an oil can to coat the connecting rod bearings and crankshaft bearings with oil so they will have some lubrication to prevent any rust and some available when you first start the engine.
I used the electric starter to pump up oil pressure until I saw oil coming from the rocker arms at the top of the heads. This helped fill all the internal passages with oil and provide some lubrication to bearings before I tried to start the engine.
I hope this is helpful. Best of success in your project.
My brother suggested I may like this blog.
He was entirely right. This submit truly made my day.
You can not consider just how much time I had spent for this information!
I’m pleased this collection of techniques I use have been helpful.
Thanks for stopping by.
1971 750/5 SWB -is there a magic trick out there to slide the seat
off the frame without taking all phillips screws out. Thx Don
Well, no. The way the hinges are mounted, you have to remove the two screws not covered by the frame tube and then rotate the hinges enough to get them off the hinge pins on the subframe. At least I haven’t found any other way.
Do you know any retailer here in the US who carries AutoSol products…?
On their web page, they list an Austin, TX PO Box and phone numbers. Why not give them a call to see if there are “distrubutors” or retail outlets that carry the product. I just order it from their web page and it shows up in a couple of days.
Thank you for posting all of this for everyone to see. I have had an R100/7 for almost a year now. It is in pretty bad condition though. So much grime all over the engine, rusted spokes on the wheels, etc. I am going to use this guide to do a refinish, and have the frame powdercoated.
Did you also refinish the cylinders? I am a little worried about those guys because I think it may be hard to get in between all of the fins.
I’m glad this helps you as you “freshen up” your ride.
I had the cylinders “walnut shell” blasted at a local shop. I emphasize “walnut shell” as glass beads can be a problem with small pieces of glass embedded in the aluminum and sand can erode the aluminum very quickly. Other options folks have used include soda blasting and vapor blasting.
I hope this helps.
Thanks for this! I am using Autosol Power Aluminium Cleaner and scrubbing this in using 3M sanding blocks (#80 so far with very positive results, and I am also going to try #150 grade). I then apply Autosol Aluminium Polish, but quite frankly the cleaner solution is working so well that the polish doesn’t really enhance the finish — though it might work to preserve the look. Looking forward to giving the back of the brake rotor carriers a good clean up too. Cheers ~ kaleuclint
Awesome. I normally would use a finer grit (00) steel wool is about equal to 180-220 grit wet/dry paper. But if the corrosion and crud is deep enough, then coarser media makes the job go quicker.
Best of success with you project.
Is there not any issue using steel wool? I’ve been told that the steel particles can embed in the casting and rust, giving a dull appearance.
Yes, that is indeed the conventional wisdom. However, I clean the surface with an aluminum cleaner and a tooth brush which seems to remove any stray bits of the wool left behind.
BTW, a quick test for any fragments of steel wool is to use a propane torch on the aluminum surface. Any steel fragments will immediately glow red and turn to rust. If you see that happening, the good news is you just “rusted” any stray bits of wool. The aluminum cleaner will remove that rust for you.
I hope that helps.
I just bought a 1976 BMW R75 with 8800 miles on it. It has been sitting all of its life. My plan is to restore it and your blog has given me lots of information that will be extremely useful.
Well, thanks for coming by and visiting. I’m glad this material is helping you get another airhead back on the road. If you have questions as your project progresses, feel free to post them on the appropriate write-up page and I and/or others will help you out.
I like cleaning the motor, transmission and the rest of cast parts before dismantling the entire bike. With the tank and seat off it’s no big deal to lay it over to each side to get beneath it. I use GUNK to get the oily residue and dirt off then an acidic aluminum cleaner/brightener such as Nice & Easy or refrigeration coil cleaner sold at Lowes. That stuff is applied diluted to a wet surface then brushed about until the foaming stops which signals it’s time to be rinsed off. Those make the cast parts look like new with little effort and in record time. The remaining cleaner can be diluted more for use on smooth aluminum to remove their lighter oxidation so less polishing is required to shine those up. I’m currently using the coil cleaner bought from Lowes since a gallon of that is cheap and also use it to clean the coils on my HVAC outside and indoor coils plus my vehicles with aluminum finned radiators.
Thanks for sharing.
Great blog. I have a R75/5 that I am about to do a top end job and some other restoration work. I bought my BMW in Dusseldorf Germany in 1977 and rode it around Europe for 4 months before shipping it hoe. The dude I bought it from over there rode this bike from Germany to India and back. I have had it coast to coast and up to Alaska. I semi-retired the bike when one of my girlfriends freaked out on me about safety and bla blah blah. She’s out of the picture now…hahaha
I am impressed with the before and after photos of the aluminum castings and metal work.
Question: Is there some magic product to apply to te brightened metalwork to preserve the restored finish? I hate to do all that work and then have the aluminum discolor again in a short time.
Also, do you have any recommendation on parts suppliers for top end rebuild, front fork rubber covers, miscellaneous supplies?
Thanks for your effort to document all of this!!!! WOW
Roberto in Michigan
Thanks for the kind words and stopping by the site.
I have used Autosol Aluminum Protectant spray. It seems to reduce the dulling of the aluminum finish. That said, it’s the nature of metal to oxidize and collect crud if a bike is ridden. It’s okay 🙂 If it really gets bad, it’s time to clean it up again.
I have a “Resources” page here:
For head work I have used Randy Long at Long’s Mechanical Services. Ted Porter’s Beemer Shop and Anton Largiader also provide this I believe:
If you wish to do the head work yourself, Ted, Anton and Tom Cutter at rubber chicken racing garage (rubberchickenracinggarage.com) can provide parts. Note machining valve seats does require knowledge about airhead requirements that most auto machine shops lack. Most BMW motorcycle dealerships sell all airhead parts that are still available from BMW as well. I like to use MAX BMW parts fiche to find what I need (http://www.maxbmwmotorcycles.com/fiche/PartsFiche.aspx) and order from them as well.
I hope this helps.
thoroughly enjoyed this piece and has given me the impetus to give my R80 the elbow grease it needs. Unfortunately some of the products you guys use are not available here on the emerald isle and I end up looking for an equivalent which sometimes gives interesting results.
Is there a surefire method for cleaning oxidation on the fins, or rather where should I start.
Greeting from sunny Wexford, Ireland
Thank you for dropping by and reading this material. I’ve been able to order directly from AutoSol. They are in Germany, so they may/should be able to ship to Ireland. Or, you could just plan a nice little trip to visit them, 🙂
I have removed the cylinders, and took them to be blasted at a local motorcycle shop to clean in between the fins. Walnut shells or “soda” are good media to ask them to use. It was not very expensive here in the US. I have not tried doing this by hand.
A search with Google, “tool to clean motorcycle cylinder fins”, shows a number of approaches to try with the cylinders on the engine. There are some brass wire wheels with fine wires (no info on who makes these), scotch-brite pads wrapped around a flat paint stir stick and scrubbing between the fins. I hear a very nice finish is achieved using “vapor blasting” which is very popular in the UK, but only recently showing up here in the US. I suspect you can find a shop with a vapor blaster that would do the work with the cylinders off the engine.
I hope this helps
Amazingly great information that you provide. As a mechanic for over years it is still helpful to hear other approaches to maintaining our BMW’s. My 1980 R100rs is kept clean, and I would love to have it shine but I prefer to have it ridden but it is a good trade off. Safe riding
I much admire all of your publishing in the public domain. I am based in South Africa and find it difficult to find such openness in what other people have found successful. If you don’t mind I would like to deal with you directly with some of my queries. I am sure that you have responded to a few of my queries related to my restoring a R75/6
I sent you a private Email.
Thanks for all the details, working process and products.
I now have my “bible” for fine cosmetic restoration!!
Cool beans. I’m glad this documentation is helpful to you.
Hi Brook –
Great info here and I will be using your techniques to restore my R100GS. What do you recommend for restoring the aluminum rim portion of the wheels? They have some oxidation/spotting and generally have a dull finish. Thanks again for your resources!
When I did that on some spoked rims, I found using the Auto-Sol aluminum cleaner and steel wool (000) worked pretty well. It takes some time particularly if you keep the spokes installed. I used some aluminum polish on them after I got the grunge and oxidation off the rims. The shine has held up pretty well.
I hope that helps.
As I continue to use your refinishing methodology as a resource for my own project I had a couple questions I hope you can answer:
– How do I ensure oxidization doesn’t come back after soda blasting, then Aluminum cleaner + steel wool, then aluminum polish?
– Do you have a process for headers that are pretty far gone? Hoping to get them back to a reflective finish, and keep them from blueing…
– Do you have a recommended frame primer and (or) paint to use after sanding rust spots?
#1 – Aluminum oxidizes almost immediately. So, you live with it. 🙂
#2 – I use Auto Sol bluing remover and elbow grease. If the oxidation is stubborn, I’ll use “0000” steel wool with the bluing remover. It there is rust, the chrome is gone. Very few places rechrome, but there are still a few in business. Google is your friend. But you can buy chrome or stainless exhaust pipes these days, so that maybe as cheap, or cheaper, then rechroming.
#3 – No. I have been powder coating my frames. Since I live in a dry climate, chips in the powder coat don’t form rust areas. That said, you can apply automotive black touch up paint to a ding and it will pretty much disappear and prevent rust from starting.
I hope that helps.
I am digging up this older article to ask you if you had any luck restoring the hand control buttons before? I know you’re a fan of forever black for the black plastic on the controls, but I would love your advice on how to get the yellow and red buttons (75′ 90/6) back to their former glory.
Was thinking about light sanding and some sort of polishing?
let me know your thoughts, and if this is addressed somewhere on your site that I am not finding!
Big fan. Many thanks. Much love. Etc.,
Well, no, I’ve not tried to restore them, so I have no advice. I assume you are talking about the /6 and later buttons that are colored yellow or red. If you find something that works well, post it here.
Hi Brook, thank you for sharing this very interesting story. I bought a 1972 R60/5 from the first owner 2 years ago and trying to restore it a little bit.
I am currently trying to clean the engine housing and did as you describe above. However I just can’t get the dark pits in the aluminium cast pores out. Tried the autosol aluminium cleaner with scott’s brite and steelwool but nothing works. Do hou have any other tips or tricks?
Thank you in advance!
Greetings from the Netherlands
Sometimes the pitting is too deep to get completely clean.
I’ve heard you can use aluminum screen door cleaner to remove stubborn oxidation from aluminum. I have not tried this, and it can cause damage if you leave it on too long.
Another idea is to use a stainless steel wire brush to break up the oxidation layer in the pores. I have found small ones here at home improvement centers like Home Depot. The larger ones sold for use by welders is much too coarse to be useful and would likely scratch the case. The small stainless steel brush is more aggressive than the scotch brite pad. Aluminum oxide is hard and if it accumulates in the pores it doesn’t want to come loose. The bristles of the stainless steel brush break it up so its easier to remove.
I hope that helps.
Hi, I want to thank you for sharing all this knowledge. I’ve owned my r75/6 for about 10 years and she just sat the past 6. I put a battery in, changed the oil, and she fired right up. I’m going to restore her this winter and be back out on the road tooling around. But I do need to give it a solid cleaning. This post was fantastic and full of great information. The only question I have is can I clean the bike without taking it apart? Or do I need to worry about corrosion of wires and things? I plan on taking it fully apart at some point, but wanted to give the bike a little shine to make it feel good in the meantime.
You don’t have to disassemble the bike to clean it up.
I don’t know the kind of climate your bike sat in. But, if it is humid and the bike was in an unconditioned space, then condensation can collect here and there. That can contribute to corrosion of the electrical connectors. That said, if the bike is running, that’s a good sign the electrical system is working too.
You can pull electrical connectors off components one at a time and look at the condition of the connector and the wiring. I would suggest doing that at the starter relay where the Red wires on terminal (30) carry all the power for the bike. I would also selectively pull a couple connectors off the spades on the connector block inside the headlight shell. If you see green corrosion, that tells you something about the need to clean the electrical connectors
sooner rather than later.
I’m pleased to hear you are going to get another airhead back on the road. 🙂
I hope this helps.
Have you found a way to restore the handlebar control lettering? There must be a way to stencil the lettering back on but I haven’t found a stencil source yet. All of the lettering on my R75/6 is gone.
I was able to do that on the carburetors, but I haven’t come up with a technique for the switch and instrument cluster lettering. That said, I hope to try some ideas this winter to see if I can come up with a way to restore the white letters.
Have you tried the ‘Forever Black’ on panniers? Or do you use something else? My panniers are looking tired so looking for a proven way to spruce them up. Thanks Mark
I have used it with good results. It’s important to clean them well before applying it. I used oil & tar remover which painters use to ensure paint surfaces are free of any oil.