… Head Guards — Fostering Adventure

Cylinder Head Guards

Crash Bars are not enough

One of the few oversights by the brilliant engineers in Germany was with regard to the cylinder heads for the boxer engine. The valve covers on those two heads protrude the furthest out each side of the bike, and because they are made from die cast aluminum, they are actually quite fragile. If the bike was to fall over and those valve covers impacted a hard surface they would fracture, and an oil leak would ensue.

You can see in this photo how much extra thickness had to be added to the outside of the tubing so it would protrude past the bump on the valve cover.

To solve this likely scenario, the engineers designed a set of very robust stainless steel crash bars that envelop the cylinder heads and valve covers. There’s just two tiny problems that they overlooked. First, the most outward point of the valve cover actually protrudes beyond the crash bars, so the valve cover could hit the ground if the bike rolled enough when falling over. Now most would say that a vast majority of bike falls would happen in difficult terrain off road, and they would probably be right. If the ground was all soft dirt or sand then there wouldn’t be an issue. But, in off road conditions, soft dirt and sand often comes with rocks embedded in them. If the rocks protrude high enough, and the bike falls in just the right place, the crash bars can encircle the rock and let it hit the valve covers. The result is a ruined day for the rider and an expensive repair.

Our solution to the Factory oversight

There are numerous companies that have created auxiliary protection devices to try and alleviate the problem of less than optimal crash bar protection. Many of them are nicely designed and fasten directly to the valve covers. However, this means that the structural support needed for these devices to protect the valve covers, is coming from… well, the valve covers themselves. Doesn’t that seem just a bit odd?

Other manufacturers make protection that is secured to the crash bars, and provides ample protection. But they seemed awfully expensive for what was essentially a stamped piece of thick sheet metal and a few clamps. Being the cheapskate that I am, I thought I could make my own solution for much less money. A lot more work, to be sure, but Covid was still running rampant and I had nothing else to do. What was nice about this little project was that most of it could be made from scrap pieces of aluminum that I had left over from other projects on the overland truck. So the only cost was a few rattle cans of paint.

The Build Process Begins

A couple of plywood slats were screwed in place to create the guide for routing the metal.

The full width of the aluminum wasn't needed, so the groove was done off centre. The length was then re-sawed to the proper width.

With the spacers now the right width, they were then cut to length.

Two of the spacers had to straddle a tubing joint, so a side slot would need to be machined.

The first step after determining just how much the valve covers protruded was to create the spacers that would rest against the crash bar tubing. For this I used a chunk of 1” x 2” aluminum flat bar, and a router with a 1” round cutter in it. A rudimentary guide fence was created to position the flat bar over the cutter, and then it was just a matter of doing multiple passes over the cutter at increasing depths until the desired dimension was obtained.

Once the spacers were finished, they were attached to the crash bars with tape so the next step of determining the size and shape of the protection plate could be determined. These plates were made from 3/16” thick 6061 aluminum plate that was also left over from other projects, and I had just enough to create both sides.

The next step took a bit of imagination so as to produce a functional piece of armour, but at the same time keep the plate as small as possible for weight reduction while also creating something that would be visually appealing to look at. Although the GS Adventure bike is often referred to as a tractor, because of its ability to walk up difficult terrain at a slow but unrelenting pace, I didn’t want my accessories to look like they were made in a farm yard.

Despite our spacers, the complex geometry of the bars had them almost touching our plate.

Once we had confirmed that our spacing cleared the valve covers, the bars were removed from the bike.

Taking the bars off the bike made shaping the plate and other bits easier.

Before we started welding things together all the bits were sanded for better paint adhesion.

Some of the pieces had to have angled edges on them to create relief for the weld metal to fill.

In order to keep the plates as close to the bars as possible, nip and cut practices were employed.

The finished cover plate had the corners removed, partially for aesthetics, but also to allow other accessories to be attached to the bars.

All of the welds were dressed down so that everything looked seamless.

In the end, the plate was held off the bars by three spacers, and the fourth side nearly touched the bar on its own.

The inside of the protection plate was uncluttered, and all welds were done only on the perimeter so the plate wouldn't show distortion.

The perimeter was shaped to try and create a smooth transition from one facet to another.

The geometry turned out to be quite complex, which is why the nip and tuck procedures were needed.

Creating the Attachment Clamps

This shows how the clamps hold the plate to the crash bars. The clamps are braced against the contoured spacer and pry down on the crash bar. For illustration, shown above is a piece of aluminum bar, held by the clamps.

Once the protection plates were finished, the next step was to create the clamps that will wrap around the back of the crash bars and hold the plate firmly in place. To do this we would once again use a piece of 1” x 2” aluminum flat bar and through a process of hole drilling and table sawing, we’d create the uniquely shaped clamps.

Once the clamps are installed, they and the contoured spacers almost fully encapsulate the crash bar tubing.

The flat bar was laid out taking in account saw cut kerfs at specific angles.

The bar had to be drilled for the 1" diameter crash bars as well as the 5/16" screws that would fasten the clamps in place.

Because I only have a small drill press, the large holes had to be drilled initially with a large step drill.

Once the 1" holes were finished, and the 5/16" holes tapped, laying out the saw cuts came next. Spacing was critical for best material usage.

With the clamps all cut out final shaping and sanding was done on the belt sanding machine.

All that remained was to transfer the screw hole locations onto the protection plates and then drill and countersink the holes.

The Final Step, Painting the parts

All three spray cans of paint were bought at a Canadian Tire Store, and can also be purchased at most auto supply shops. The brands might change, but the products are readily available worldwide.

Since the protection plates, by definition, would be taking some abuse, I wanted to coat them with something that could be easily touched up when they got marred. That meant powder coating wasn’t an option. Besides the set up costs for coating such a small amount of parts would make that form of coating quite expensive. Instead I decided to coat the parts with a gravel guard material that’s usually used for the rocker panels on cars. It’s easy, cheap and readily available just about anywhere when repairs are needed.

The first step is cleaning with a suitable material like lacquer thinner or methyl hydrate, then priming the aluminum with a special metal etching primer so it would key into the metal for maximum adhesion. For that, I used an automotive product made by Dupli-Color that was purchased at the local Canadian Tire store. The gravel guard was also purchased there along with the final coating, a flat black paint. The gravel guard has a rough finish that doesn’t look great after some exposure to the elements, and the finish didn’t match anything on the bike. So I used a flat black enamel, more of a satin black really, the finish of which almost exactly matched the mat black finish on much of the plastic on the bike. It was the perfect solution.

With the first sides primed, the remaining front faces were washed again with alcohol before priming.

All sides of every component were primed for maximum adhesion of the gravel guard.

Fortunately the spraying of the parts in the garage doesn't impact anything more than a few feet away. The light paint dries in the air, and the gravel guard doesn't mist. So overspray isn't an issue.

Even the clamps were completely coated since small parts of them would be visible.

I always spray the back sides first so there is no chance of messing up the viewable surfaces if they were done first and then flipped over.

Since the gravel guard is a textured finish, any overspray that bounced onto the outer surfaces didn't need sanding off.

All surfaces have to be sprayed many times with light coats to build up the thickness and the texture.

The texture is achieved by holding the can at various distances from the part, depending on how coarse you want the final product. Some practice is needed to perfect the technique.

The gravel guard is slow drying because of its film thickness, so several days must go by until it is hard and the top coat of enamel is applied.

The satin finish of the "flat" black is very refined and provides an even colour and sheen over the entire part.

Again, the clamps were also done on all sides so the visible parts matched the front face of the protection plates.

We were using stainless steel screws to hold things together, but we didn't want bright silver dots showing. So the screws were etch primed and painted with the satin black.

Installation

Once the paint had dried for four or five days to ensure it was hard enough to be handled without leaving fingerprints, it was just a matter of holding the plates in place and feeding the screws through the five holes into the clamps on the back. The Allen key that is used to tighten the flat head screws can sometimes chip the paint on the edge of the hex holes, so those often have to be touched up by spraying a bit of the paint into a small dish and then dabbing on the touchup with a tiny paint brush. When it dries it can’t be seen.

With this plate all but installed, all we have left to do is screw in the last flat head fastener.

A small piece of tough foam strip is attached to the inside of the protection plate to take up the gap between it and the crash bar.

You can see here why it was necessary to paint the clamps to match the outside of the protection plate. All is visible.

You can see here how the clamps function inside the assembly, and also how the front contoured spacer grips the forward tube of the crash bar.

The shaped and mitred corner nicely wraps around the bend in the crash bar tubing.

This shows one of the reasons the protection plate was sculpted in the four corners. It allows for an additional support brace to be attached to the crash bar.