51 BMW 1983 R80ST Refinish Aluminum Engine Block

This “project bike” spent some time outside and was covered in oil and grease from leaking seals when I got it. So the engine block, along with many other parts, looked pretty bedraggled.

Engine Block & Transmission When I Found The Bike

Engine Block & Transmission When I Found The Bike

Engine Block When I Found The Bike

Engine Block When I Found The Bike

Lower Left Of Engine Block When I Found The Bike

Lower Left Of Engine Block When I Found The Bike

Lower Left Of Engine Block When I Found The Bike

Lower Left Of Engine Block When I Found The Bike

Oil Pan And Bottom Of Transmission When I Found The Bike

Oil Pan And Bottom Of Transmission When I Found The Bike

I have gotten a number of questions from readers over the years about how I refinish the aluminum engine block (and the transmission and rear drive aluminum cases). I don’t bead blast the engine as that requires complete disassembly of the engine and laborious cleaning of all the internal oil passages in the block. Instead I use a secret ingredient, a lot of elbow grease, along with various abrasives and Auto Sol Aluminum Cleaner.

When I restored the 1973 R75/5, I put together a document showing the techniques I use to refinish various parts.

I also put together a document on refinishing, repairing and painting when I rebuilt the 1983 R100RS and converted it into an RT.

For this R80ST rebuild project, I decided to shoot a video showing how I refinish the engine block. The products and techniques I use are also applicable to the cast aluminum transmission and rear drive cases. If all you want to accomplish is to refinish the cases, you can do that without disassembly of the transmission or rear drive.

Tools

As I mentioned earlier, the most important tool is elbow grease and a mental attitude that I can summarize as:

Endeavor to Persevere

This work can be tiring so I don’t try to do it all in a single effort. Instead, I work on the engine block for awhile over several days and quit when my arms get tired or my motivation wanes.

Besides a good mental attitude, I use a variety of brushes and Auto Sol’s Aluminum Cleaner. I have stainless steel brushes, a green Scotch Brite pad, brass brushes, “0000” steel wool and nylon brushes. I use blue shop towels to wipe off the dark residue after working on the block with aluminum cleaner. As a final step to remove any trace of dark aluminum residue from the aluminum cleaner, I use brake cleaner and a clean blue shop towel to get the engine block shiny clean.

NOTE:
I got these brushes at Home Depot, but you can find similar brushes in most hardware stores.

Aluminum Refinishing Tools (Left To Right): Nylon Brush, "0000" Steel Wool, Brass Brush, Green Scrubby Pad, Stainless Steel Brush, Brake Cleaner, Aluminum Cleaner

Aluminum Refinishing Tools (Left To Right): Nylon Brush, “0000” Steel Wool, Brass Brush, Green Scotch Brite Pad, Stainless Steel Brush, Brake Cleaner, Aluminum Cleaner and Gloves

Stainless Steel Brush

Stainless Steel Brush

Green Scotch Brite Pad

Green Scotch Brite Pad

Brass Brush

Brass Brush

"0000" Steel Wool

“0000” Steel Wool

Auto Sol Aluminum Cleaner

Auto Sol Aluminum Cleaner

Blue Shop Towel With Black Residue From Aluminum Cleaner

Blue Shop Towel With Black Residue From Aluminum Cleaner

Brake Cleaner

Brake Cleaner

WARNING
I wear rubber gloves when working to keep the aluminum cleaner and brake cleaner off my skin.

Video

Here is a short video summarizing the procedure and the final result that’s very close to the factory original patina.

VIDEO: 1983 BMW R80ST Refinish Aluminum Engine Block

Degrease The Bike

I start by cleaning all the oil, grease and crud off the bike using Gunk Foamy engine cleaner. I used three cans of the foamy engine cleaner to get a lot of the the baked on oil and grease off the bike. It was pretty filthy.

Gunk Foamy Engine Cleaner

Gunk Foamy Engine Cleaner

I use a nylon brush to loosen the crud and if it’s really baked on I use a stainless steel brush on it. I applied the engine cleaner in the street as the engine, transmission ,rear drive and wheels were really filthy.

Ready To Degrease The Bike

Ready To Degrease The Bike

Applying Engine Degreaser To Under Side

Applying Engine Degreaser To Under Side

Rear Drive Looking Cleaner

Rear Drive Looking Cleaner

Left & Front Of Engine Looking Cleaner

Left & Front Of Engine Looking Cleaner

After Degreasing The Bike

After Degreasing The Bike

After Degreasing The Bike

After Degreasing The Bike

Degrease the Engine Block

After I removed the engine from the frame and the top end off the engine block, there was still a fair amount of baked on oil on the block, so I use the Gunk Foamy engine cleaner, a steel brush to get it off and a paint scraper on the shelf at the rear of the engine block that’s under the transmission as the oil and gunk was very thick there.

Left Side, Lower Block Still Filthy

Left Side, Lower Block Still Filthy

Shelf At Rear Of The Block Was Filthy With Thick Gunk I Removed With A Paint Scraper

Shelf At Rear Of The Block Was Filthy With Thick Gunk I Removed With A Paint Scraper

Right Side, Lower Block Still Filthy

Right Side, Lower Block Still Filthy

The Foamy got most of the gunk off the engine block. When I removed the top engine cover there was some oil and dirt at the top of the engine block underneath the cover. I used the Gunk pump spray engine cleaner and a nylon brush to remove that.

Gunk Engine Cleaner

Gunk Engine Cleaner

Using Nylon Brush To Scrub Engine Cleaner Into Baked On Oil

Using Nylon Brush To Scrub Engine Cleaner Into Baked On Oil

Here is the degreased engine block at this point.

Rear Engine Block Degreased

Rear Engine Block Degreased

Lower Left Block Getting Cleaner

Lower Left Block Getting Cleaner

Lower Right Of Block Getting Cleaner

Lower Right Of Block Getting Cleaner

Refinish The Aluminum Engine Block

Before I start, I plug the push rod tube and oil filter holes to keep debris out of the engine.

Plugging Push Rod Tube And Oil Filter Holes To Keep Debris Out

Plugging Push Rod Tube And Oil Filter Holes To Keep Debris Out

There are a lot of dark spots of hardened aluminum oxide in the pores of the casting.

Dark Spots At Top Right Side

Dark Spots At Top Right Side

Dark Spots Around Push Rod Tube Holes On Lower Right Side

Dark Spots Around Push Rod Tube Holes On Lower Right Side

Dark Spots Around Push Rod Tube Holes On Lower Left Side

Dark Spots Around Push Rod Tube Holes On Lower Left Side

I start with the brass brush and spray a little aluminum cleaner and work it with the brush. Then I clean the black residue off with a blue shop towel and inspect the aluminum.

Applying Small Amount Of Aluminum Cleaner

Applying Small Amount Of Aluminum Cleaner

Using Brass Brush With Aluminum Cleaner

Using Brass Brush With Aluminum Cleaner

I continue working on these areas with the brass brush and aluminum cleaner. If I can’t remove the dark spots of aluminum oxide I switch to the stainless steel brush in tight areas and the green Scotch Brite pad in larger areas. Then I repeat brushing the case with the brass brush and clean off the black residue with a blue shop towel.

Removing Aluminum Cleaner Residue

Eventually the darker spots look like they are pretty faint and I switch to the “0000” steel wool pad and scrub the block with it and aluminum cleaner. The steel wool creates a nice patina on the aluminum and also gets bits of dark aluminum oxide out of the nooks and crannies of the casting.

NOTE:
If bits of steel wool are left behind, they will rust and create brown spots in the aluminum. I thoroughly clean the engine block with aluminum cleaner and brake cleaner so I remove all the small bits of steel wool.

Using Steel Wool

At that point I use the brake cleaner and a clean blue shop towel and wipe down the case to remove the last traces of dark residue. It’s not uncommon to see that some of the dark spots I thought were gone, show up again, but they are fainter, so I’m making progress.

Black Aluminum Oxide Spots Still There, But Much Lighter

Black Aluminum Oxide Spots Are Still There, But Much Lighter

So I use the stainless steel brush on the small spots with a bit of the aluminum cleaner. Then I finish up with the aluminum cleaner and the brass brush followed by the “0000” steel wool again.

After a couple repetitions of this procedure, and a final application of brake cleaner, the engine block has an almost factory original patina again.

After Steel Wool

After Steel Wool On The Upper Part Of The Engine Block

Applying Brake Cleaner

Applying Brake Cleaner

Patina Of Aluminum Engine Block Looks Close To Factory Original

Patina Of Aluminum Engine Block Looks Close To Factory Original

There are some nicks, gouges and scratches on the block that can’t be removed, but the rough casting areas are clean once again. I’ll clean out the inside of the bell housing where the clutch and flywheel are located when I replace the clutch, the rear main seal and the oil pump cover O-ring.

Final Product

Here is the refinished engine block. I estimate it took me about 10 hours over five days to complete the work.

NOTE:
I have not refinished the front engine cover nor removed the red paint and refinished the oil pan yet.

All Done-Left Side

All Done-Left Side

All Done-Left Side

All Done-Left Side

All Done-Rear

All Done-Rear

All Done-Right Side

All Done-Right Side

All Done-Right Side

All Done-Right Side

6 thoughts on “51 BMW 1983 R80ST Refinish Aluminum Engine Block

  1. just a note about cleaning grease off in the street. this is illegal in most european countries and in south africa. also admire the finish you achieved but the patina of age is lost. it all looks too new.

  2. As always phenomenal attention to detail and exceptional planning so that one can follow the steps. Which I did on a few occasions. I’d like the results because in natura it looks very much like a old cleaned bike. If used right, meaning driven, in a year and will have an even tan.

  3. Brook, thank you for the timely (in my case) and very interesting video? Do you have a source for the Autosol aluminum cleaner currently? I have googled it a bit and do not see it in stock in the US anywhere.

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