51 BMW 1983 R80ST Repair, Refinish & Paint

This document consolidates the work I do to repair, refinish and paint parts during the rebuild of the 1983 R80ST.  Let me explain how I use the terms.

  • Repair: Fix something that is broken; not the same as parts replacement.
  • Refinish: Restore the finish, typically of aluminum castings, to factory condition
  • Paint: Strip and paint parts often to match the factory paint. This does not cover professional painting and powder coating.

Some sections of this document have links to a separate document, or section of a document, I published. Other sections contain original material.

Resources

I published a document summarizing various techniques, products and tools I use to refinish parts on my projects and I also published a similar repair, refinish and paint document for the 1983 R100RS conversion to an RT project. You can review this material here:

Robert Fleischer, aka, “Snowbum” published material on care, repair and refinishing techniques, materials, etc.

Repair & Refinish Crankshaft Guide Ring

The guide ring fits on the rear crankshaft nose. The rear main seal rubs on the guide ring to keep oil from leaking down the crankshaft into the bell housing where the clutch is installed. This engine has about 63,000 miles on it so there is a groove worn into the guide ring from the rear main seal. This groove was not too deep so I used 600, 1,000 and 1,500 grit wet/dry paper to sand the sealing surface of the guide ring until I couldn’t feel the groove with my finger nail. I also use Auto Sol metal polish to clean and polish the guide ring before reinstalling it.

Groove Worn Into Guide Ring By Lip Of Rear Main Seal

Front Of Guide Ring

Rear Of Guide Ring

Cleaned Up Guide Ring Front Face

Cleaned Up Guide Ring Front Face

Sanded And Polished Guide Ring Has Faint Groove, But I Can't Feel It With My Finger Nail

Sanded And Polished Guide Ring Has Faint Groove, But I Can’t Feel It With My Finger Nail

Cleaned Up Guide Ring Rear Face

Cleaned Up Guide Ring Rear Face

Refinish Aluminum Engine Block

This document shows how I do this and also has a video showing the technique I use to refinish the engine block and is how I refinish other cast aluminum parts: the front engine cover, transmission case, and rear drive case.

Refinish Front Engine Cover

After I degreased and washed the front engine cover I could see that it had a lot of corrosion. This is not uncommon for the front cover as it gets hit with sand, dirt and water spray contributing to corrosion of the aluminum

Front Engine Cover Corrosion

Front Engine Cover Corrosion

Front Engine Cover Corrosion

Front Engine Cover Corrosion

Front Engine Cover Corrosion

Front Engine Cover Corrosion

The inside shows oil from a leaking camshaft seal. Also, there are traces of the red paint a previous owner painted it with.

Inside Front Engine Cover Showing Oil From Leaking Camshaft Seal

Inside Front Engine Cover Showing Oil From Leaking Camshaft Seal

Front Engine Cover Red Paint From Previous Owner

Front Engine Cover Red Paint From Previous Owner

Front Engine Cover Markings: Casting Number At Left (Not Part Number)

Front Engine Cover Markings: Casting Number At Left (Not Part Number)

So I used the “big gun”, my Harbor Freight bead blast cabinet that a good friend gave to me. It is designed to sit on a bench top, but mine has castors on it so I can wheel it around. I never use it inside my shop because it creates a lot of very fine glass dust (look under the wheels in the picture below) that escapes the cabinet and that’s the last thing I want in the shop.

The Big Gun: Harbor Freight Benchtop Bead Blast Cabinet

The Big Gun: Harbor Freight Benchtop Bead Blast Cabinet

Inside Harbor Freight Benchtop Bead Blast Cabinet

Inside Harbor Freight Benchtop Bead Blast Cabinet

It took me about 3-4 hours to get rid of the corrosion and refinish the cover. My compressor is not big enough to supply air flow at 80 PSI to the blast cabinet so I have to let it rest every 20 minutes or so to let it cool off as it runs continuously when using the blast cabinet. That said, I find that about 50 PSI gives a nice finish to the cover. So when I have a stubborn spot of corrosion, I let the compressor fully charge the air tank at 120 PSI. That is strong enough to remove any stubborn spots.

With patience, coffee, and time on my hands, I get rid of all the spots of corrosion on the front engine cover.

Making Progress, But I Can Still See The Spots Of Corrosion

Making Progress, But I Can Still See The Spots Of Corrosion

Looking Much Better

Looking Much Better

After blasting the hardened corrosion off the front engine cover, I wash the cover in hot water using a tooth brush and dish soap to remove any bits of glass and dirt left behind.

Then, as I show in the Refinish Aluminum Engine Block section above, I use Auto Sol aluminum cleaner with a brass brush and brush the cover. I remove the black residue with a blue shop towel. That is followed by more aluminum cleaner with steel wool and blue shop towels to remove the residue until to get the patina I want. Then I clean it with brake cleaner and more clean blue shop towels to arrive at the finish shown below.

Refinished Front Engine Cover

Refinished Front Engine Cover

Refinished Front Engine Cover

Refinished Front Engine Cover

Refinished Front Engine Cover

Refinished Front Engine Cover

Inside Refinished Front Engine Cover

Inside Refinished Front Engine Cover

The engine block casting is rougher than the front engine cover, so the engine cover appears a bit brighter than the engine block after refinishing them.

Comparing Engine Block To Front Cover: Cover Is Has A Finer Casting So More Shine

Comparing Engine Block To Front Cover: Cover Is Has A Finer Casting So More Shine

Paint Inner Timing Cover

The 1983 model inner timing covers are painted black. This one needed repainting. I bead blasted the cover to remove the loose paint. The cavity where the timing chain and crankshaft and camshaft timing sprockets reside was in good condition so I did not repaint that part of the timing cover.

Inner Timing Cover Before Bead Blasting

Inner Timing Cover Before Bead Blasting

Inner Timing Cover Before Bead Blasting

Inner Timing Cover Before Bead Blasting

Inner Timing Cover Before Bead Blasting

Inner Timing Cover Before Bead Blasting

Inner Timing Cover Before Bead Blasting

Inner Timing Cover Before Bead Blasting

I used 1/8 inch pinstripe tape to mask off the sealing surface of the cover, the mounting boss for the alternator stator, and masking tape to seal off the electronic ignition sensor hole and the bosses for the mounting bolts. I also masked off the bosses of the holes the diode board mounts to to ensure a good ground for the diode board. I used some M6 bolts and threaded them into the holes in the timing cover to protect the threads from paint.

1/8 Inch Pinstripe Tape

1/8 Inch Pinstripe Tape

Applying Tape To Exterior Ribs Of Inner Timing Cover

Applying Tape To Exterior Ribs Of Inner Timing Cover

As shown in the picture below, the right side of the inner timing cover has a cut-out for the frame tube. The ribs in the cut-out are all black, so I don’t tape them.

Inner Timing Cover After Removing Loose Paint And Taping Ribs

Inner Timing Cover After Removing Loose Paint And Taping Ribs

Tape Applied To Electronic Ignition Sensor Hole & Bolt Holes

Tape Applied To Electronic Ignition Sensor Hole & Bolt Holes

Applying Paint To Alternator Stator Housing Boss

Applying Paint To Alternator Stator Housing Boss

Tape On Alternator Boss

Tape On Alternator Boss

M6 Bolts To Keep Threads Clean

M6 Bolts To Keep Threads Clean

Tape On Diode Board Hole Bosses

Tape On Diode Board Hole Bosses

Tape On Timing Chain Cavity

Tape On Timing Chain Cavity

I use brake caliper paint and bake the painted parts in my oven at 250 F for 25 minuets to cure the paint and harden it.

Inner Timing Cover Ready To Paint

Inner Timing Cover Ready To Paint

Inner Timing Cover Drying With Tape Removed

Inner Timing Cover Drying With Tape Removed

Tape Removed From Inner Timing Cover

Tape Removed From Inner Timing Cover

Tape Removed From Inner Timing Cover

Tape Removed From Inner Timing Cover

Tape Removed From Inner Timing Cover

Tape Removed From Inner Timing Cover

Paint Top Engine Cover

The top engine cover is black with the BMW letters unpainted. A previous owner painted over the black paint with blue paint. Most of the paint had pealed.

Top Engine Cover Before Bead Blasting

Top Engine Cover Before Bead Blasting

Top Engine Cover Before Bead Blasting

Top Engine Cover Before Bead Blasting

Top Engine Cover Before Bead Blasting

Top Engine Cover Before Bead Blasting

Top Engine Cover Before Bead Blasting

Top Engine Cover Before Bead Blasting

I bead blasted the cover to remove some of the blue paint a previous owner had used to paint the cover and to remove loose paint on the inside of the cover.

Top Engine Cover After Bead Blasting

Top Engine Cover After Bead Blasting

Top Engine Cover After Bead Blasting

Top Engine Cover After Bead Blasting

Top Engine Cover After Bead Blasting

Top Engine Cover After Bead Blasting

Top Engine Cover Markings

Top Engine Cover Markings

I masked off the BMW letters using 1/8 inch pin stripe paint. After I removed the pin stripe tape, I used some 600 and then 1000 grit wet/dry paper to clean up some bits of paint and to polish the letters.

Applying 1/8 Inch Pinstripe Tape To Letters On Top Engine Cover

Applying 1/8 Inch Pinstripe Tape To Letters On Top Engine Cover

Tape Removed From Letters Of Top Engine Cover

Tape Removed From Letters Of Top Engine Cover

Top Engine Cover After Painting

Top Engine Cover After Painting

Vapor Blasting

Vapor blasting mixes water with glass beads and aluminum oxide. It creates a “like new” patina on aluminum. I use Vintage Twins in Arvada, CO to do this work. They have a professional vapor blast cabinet and a sub-division called Colorado Vapor Blasting.

Cylinders

Here are before and after pictures of the cylinders.

Left Cylinder Removed-Pretty Grungy

Left Cylinder Removed-Pretty Grungy

Vapor Blasted Cylinders

Vapor Blasted Cylinders

Vapor Blasted Cylinders

Vapor Blasted Cylinders

Vapor Blasted Cylinders

Vapor Blasted Cylinders

Fork Lower Sliders

The lower fork sliders were painted blue by a previous owner. Here are the before and after pictures.

Forks Removed And Labeled With Previous Owner Applied Pealing Blue Paint

Forks Removed And Labeled With Previous Owner Applied Pealing Blue Paint

Vapor Blasted Lower Fork Sliders

Vapor Blasted Lower Fork Sliders

Vapor Blasted Lower Fork Sliders

Vapor Blasted Lower Fork Sliders

Revisions

2022-03-26  Add repair of guide ring.
2022-04-10  Add painting top cover, inner timing cover and vapor blasting.

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