Checking for a bent frame

If you are rebuilding, repainting, or restoring, it is highly advised to inspect the frame for bends. If you know (or suspect) that the bike was involved in a crash, or if the bike rides crooked (rides straight but the bars are cockeyed to one side), if it takes more effort to turn left vs. right (or vice versa), or if, when riding the bike down a straight and level road, the bike is leaned one way or the other in order to make it track straight, you must inspect the frame. Something is probably bent. 

Now it could be your frame is bent.  Or it could be the fork, or front or rear swingarm.  Or the handlebars could be bent. This procedure only focuses on determining if the frame is bent. 

This procedure is well documented in the Barrington manual, which is a highly recommended book for mechanics of vintage BMWs. 

First obtain two straight tubes or rods. One must fit through the steering tube. A fork tube works nice for this. The other must fit through the rear swingarm pivots in the frame. I went to the local metal yard and picked up some stainless steel tube for this, but anything strong and straight will work well.

Next you'll need a carpenter's square, a C-clamp and a few bungie cords. 

Arrange the smaller diameter rod through the rear swing arm pivots and bungie in place. You want to ensure that the rod is pulled in the same direction on both sides so that it sits square to the travel line of the bike. Bungie it in place. Now clamp the square to the rod so that you have a perpendicular reference. Arrange the square so that it is positioned in the "window" of the battery tray. See photo below. Click to enlarge photo. 

What is important here is that the carpenter's square gives you a good perpendicular reference to the plane formed by the rear swingarm pivots, and also that you can see the reference in the window of the battery tray.  (See photo below).

Now arrange your larger reference straight tube through the steering head and bungie it in place. Again you want to ensure that the tube sits square on the upper and lower bearing race lands in the same spot. I think it's easy to pull it back towards the back of the bike, and then bungee cord it in place. (See photo below.)

Now that you've done this, you can compare the two vertical lines formed by the carpenter's square and the tube going through the steering tube.  If it is not exactly lined up, check your reference tube positions to be sure they are positioned correctly, and check your square to be sure it is settled in place. 

If the frame appears to be bent, then you'll need to take the next step which is to take the frame to an alignment shop and have it measured with professional equipment, and straightened, if necessary. 

Aluminum Cylinder Head Fin Repair

BMW Cylinder heads have cooling fins that are notorious for getting bent and broken. Scottie's Workshop can repair your broken and bent fins. Here are some before and after photos of some damage repaired on a RHS R69S cylinder head. Ask us about our repair services!

BEFORE:

AFTER:

Scottie's Workshop is a full service BMW machine shop. Call us for all your repair needs: crank repair, cylinder heads repair and rebuilding, transmission repair and rebuilding, final drive rebuilds, precision welding and more. 

Laney's 7500 mile all original R69S

Laney's lovely R69S is in the shop for a solo seat, and Service II. This machine has 7,800 original miles on it!! All the wires, control cables and straps are factory original and in their original positions! Yes, we took photos!

Wes' R60/2 with Ural Sidecar restoration project is complete!

Wes' R60/2 with Ural sidecar restoration is complete!  This was an extensive restoration project that also included the sidecar.  All components were restored, refurbished or improved. The chassis was straightened, bike and hack body work straightened, painted and striped. The brake system was upgraded with Vintage Brake 3000 material and the hub turned. The engine was rebuilt with a full crank rebuild.  New pistons, bores, heads , carbs, FD and transmission - all rebuilt.

I also gave Wes the 1st Place Plaque that this bike won at the 2014 European Motorcycle Show. I took the bike to the show last month and Wes was really surprised that he was able to take the bike home and a 1st place prize! 

This was a very fun project and I am delighted with how the bike and side car turned out!

Media Blasting Aluminum Cases

When refurbishing a motor, or an entire bike, it is often desired to improve the cosmetic appearance of the cast aluminum cases. There are several cast aluminum parts on the bike that benefit from being media blasted and those include:

1. Engine block, timing cover (intermediate case), electrics cover (front cover) and the semi-circular door on the top of the engine,
2. Heads and valve covers,
3. Transmission case and door,
4. Wheel hubs.

Many owners blast the bottom of the rear shocks and then paint them or clear coat them. However I prefer to have them cadmium plated. When cadmium plating, I do not blast them; I just send them off and have the plater take care of it. 

Scottie's workshop always media blasts cylinder heads when they are disassembled for refurbishing  and machine work during a head service or repair. We also blast the valve covers so they come back to the customer matching the newly cleaned cylinder heads. 

Because valve covers do not have any crevices, they can be media blasted without special consideration, so long as they are cleaned thoroughly after blasting to remove any residual media. 

Wheel hubs can be blasted only during a wheel rebuilding service.  Prior to building, the bearings and old spokes are removed and the braking surface is protected with masking tape. Then the wheel can be rebuilt. Once the wheel is spoked and trued, then the braking surface can be trued on a lathe.

Blasting Media

For ease of clean up and less wear on the case surfaces, I recommend using beads.

Vapor Blasting

Vapor blasting (or vapor honing) is a blasting process in which the part is media blasted with glass beads and then blasted again with a fine slurry of very small glass beads and water/chemical cleaning agent solution.  The resulting finish is stunning and far superior than blasting alone.  In addition to the fine satin finish of aluminum parts, the aluminum retains a resistance to staining.  At Scottie's Workshop, we only media blast parts that are to be powder coated or painted.  We vapor blast everything else. 

Engine and Transmission Cases

Before jumping into blasting your cases, you may want to give some thought to the end appearance of your bike after plating. For example, if you are rebuilding your transmission, and decide to blast it clean, consider how it will look when bolted back up to your motor, which may have its original patina. 

When refurbishing and/or restoring a /2, we will normally media blast all the cast aluminum, or we will blast none of it, preferring instead to "deep clean" and preserve the original patina as best as possible. I discuss deep cleaning in another article. 

The following photo illustrates a freshly blasted transmission case next to a deep cleaned, natural patina engine block. 

When media blasting cases, the primary risk is media contamination into the case.  By its very nature, media is highly abrasive and durable stuff and will immediately destroy the surfaces of  even hardened, machined parts, such as bearing races and gear faces.  You will never be able to clean out all the media. The size of the media, and the number of places it can hide inside the cases, even after deep cleaning, soaking and rinsing of the cases, there will always be a risk of contamination.  There are still folks out there destroying their engines and transmissions because of residual media left inside the case. When it comes to media blasting open cases, the answer is clear.  Don't do it! 

So how do you media blast a case without risking contamination. The answer is to seal the cases before media blasting.  Here's how we do it at Scottie's Workshop.

For the case, we use 1/4" polycarbonate sheet to make up some doors for the engine case openings. The base gasket serves as a handy template for tracing and cutting. 

RTV and base gasket nuts (and some washers) are used to seal the poly to the case.

The transmission (studs removed) makes a handy template for tracing and cutting a door for the bell housing. RTV and nuts and washers are used to seal the poly to the case.

The semi-circular door on top is sealed with RTV and tightened down. Other holes are sealed with rubber bungs, or aluminum plugs made on the lathe, as shown in the photo below.

On the transmission bench, my friend Blaise Descollonges has come up with a novel method to seal the many circular-shaped openings of the transmission case. 

Bungs were cut on a lathe from aluminum.

The bungs have beveled edges so that they seal air tight. 

The transmission door is sealed with RTV and a gasket.

The end result is that these aluminum cases can be safely media blasted without risk of contamination. 

Even so, we thoroughly wash and rinse the cases several times with soap and water using a garden hose and high pressure washer after media blasting to ensure that any residual media is washed away. 

The end result is worth the effort: clean and refurbished -- and beautiful! - cases! 

When having your /2 serviced or restored at Scottie's Workshop, ask us about our media blasting services!

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Addendum, I was over at Joe's shop building a motor and I decided to use some of Joe's blasting plugs since I was there. They were so nice and clever, I decided to take a picture and update this article.