- Repair & Refinish Crankshaft Guide Ring
- Refinish Aluminum Engine Block
- Refinish Front Engine Cover
- Vapor Blasting
- Powder Coating
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.
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.
- Robert Fleischer: Cleaning exhaust systems; Drilling/cutting/repairing windshields; Noisy fairings/dash; Pesky hollow rivets; Cleaning plastic visors & windshields; Washing the bike; Maintaining the paintwork & aluminum; Sandblasting, Vapor blasting; Bent levers; Repairing fairings & luggage (hard bags); Black plastic & rubber trim
- Robert Fleischer: Chemicals; Oils (not for engine, driveshaft, gearbox & rear drive); Assembly Lubes, Additives, Greases (including spline greases); Loctite, Sealants, Adhesives; Anti-seize Compounds; Electrical Contact Treatment; Waxes; Wheel paint; Tank Coatings; Windshield and visor maintenance; Removing sticky labels and residues; Cleaners (for your hands & for engine parts, etc.); Freeing up rusty fittings (nuts, bolts, etc)
- Robert Fleischer: Luggage, Tank Bags, Windshields, Mirrors, Instruments, etc.; Locks & Keys (except fuel caps); Noisy fairing vibration at the upper dash
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.
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
The inside shows oil from a leaking camshaft seal. Also, there are traces of the red paint a previous owner painted it with.
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.
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.
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.
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.
I paint a lot of the small parts that need to be refreshed. I have the tank, fenders and side covers painted by a local professional painter.
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.
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.
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.
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.
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.
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.
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.
I bead blast the valve covers to remove the orange paint a previous owner applied over the original black paint. After I finish painting them with gloss caliper paint I use a single edge razor blade to clean the paint off the center bars and then use 600 grit wet/dry paper and a wood block to clean up and polish the center bars.
Here are some pictures of the work.
I bead blast the airbox to remove the loose paint. Then I paint it with the same gloss black caliper paint I used on the inner timing and top engine covers and the valve covers.
Here are some pictures of the work.
The BING carburetor badges are black and have raised printing that is painted white. I refresh the badges using white pin stripe paint. You read about how I do this here.
Here are some pictures of before and after.
Miscellaneous Small Parts
I repaint a lot of the smaller parts that need to be refreshed. I clean them, use a wire wheel to remove any loose paint, and if necessary, I paint them with an etching primer and the a color coat. I typically use caliper paint and after it has dried for a day, I bake the parts at 200 F for about 30 minutes to cure the paint.
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.
Here are before and after pictures of the cylinders.
It was pretty grungy and had been painted orange by the original owner.
I replaced the spokes on the wheels with stainless steel spokes and had the hubs and rims vapor blasted. Here are some before and after pictures.
Fork Lower Sliders
The lower fork sliders were painted blue by a previous owner. Here are the before and after pictures.
I disassembled the transmission, cleaned it with engine cleaner and had the case and rear cover vapor blasted. Here is the before and after.
After vapor blasting.
Repair Transmission Cover Mating Surface
There was corrosion on the mating surface and I filled it in with some JB Weld and leveled it and smoothed it.
After removing the rear drive, I had it vapor blasted.
I have the frame, rear sub-frame, center stand, swing arm and battery box powder coated at Powder Coating Specialties. I used 90% gloss for the powder coat.
Before taking the parts to them, I mask off areas with masking tape that I don’t want powder coat on. I use some green garden wire and wrap it through threaded holes that I don’t want powder coat inside of.
Here are some before and after pictures.
My son repaired the center stand and reinforced it before I had it powder coated.
2022-03-26 Add repair of guide ring.
2022-04-10 Add painting top cover, inner timing cover and vapor blasting.
2022-05-24 Add painting air box, valve covers, powder coating section.
2022-12-20 Add vapor blasting transmission, rear drive, oil pan and wheels.
2022-12-21 Add Paint Miscellaneous Small Parts & Carburetor Emblems.