By Dave Porter, Customer and Technical Support at The Bonneville Shop
Occasionally I receive inquiries from customers stating a part that was purchased from The Bonneville Shop does not fit correctly. I typically query the customer about the application, including make, model, and year. Sometimes it is revealed that the part was ordered in error, and the result is a simple return of the part.
Other times, the correct pattern parts were ordered for the specific application, but still does not fit correctly as it is, without making some adjustments. In other words, the part is not in a “state of fine fettle”, which by definition means the state of condition the part needs to be in. It can be the way the part is manufactured and finished, or the condition of the accompanying part it is being fitted to may be excessively worn or compromised.
For those of you that have been around vintage machines for some time, this will come as no surprise that there are often occasions where “fettling” is required to get the set of parts to fit together correctly. This can involve sanding or filing to remove a small amount of material, grinding to remove a larger amount of material, drilling oversize holes, elongating slots, etc. Considering that much of the tooling and machinery that was used to manufacture factory original British motorcycle parts was worn out or reworked after the second World War, it is no surprise that today’s reproduction parts, often manufactured in modern facilities, will require some careful adjusting to fit and finish the installation.
Sheet metal items such as mudguards, petrol tanks, side panels, and chainguards almost always require some fettling. Other components that are formed, bent, and welded together to form an assembly, such as exhaust pipes, main stands, and grabrails are also subject to various types of adjustments to achieve a proper fit on the motorcycle.
We, as vintage British motorcycle enthusiasts are fortunate to be served with such a large aftermarket of reproduction parts to keep our old motorcycles running and looking good. Some of our suppliers even use the original tooling for manufacturing replacement parts to original specifications (as closely as possible). Many pattern parts originating from Asia are also excellent reproductions, an example being the Emgo-branded fork stanchion tubes.
“For those of you that have been around vintage machines for some time, this will come as no surprise that there are often occasions where “fettling” is required to get the set of parts to fit together correctly.”
When visiting the various online forums dedicated to the preservation of vintage BSA, Norton, Triumph, and other motorcycle marques, I am frequently met with disparaging comments and opinions about the quality and fitment of today’s reproduction pattern parts, but considering the choices we had back in the mid-1980s, before the growing revival of interest in vintage British motorcycles, we should be thankful that options exist now that go beyond the well-used or new-old-stock parts that were hard to find in the pre-internet days.
Today, as in the past, the installer becomes the fitter. Working on these old motorcycles has always been somewhat challenging, even for the assemblers on the production lines 60 years ago. Considering the manual labor that went into the production of each and every one of these old bikes, it’s not really a stretch to consider them “hand-built”.
Now that I have introduced the notion that new reproduction pattern parts often need adjustments, let’s get onto some of the tools that are called on for fettling. We offer a large selection of mudguards in our catalog, with the majority of them being undrilled. Accurately drilling the fenders for fitment to a motorcycle requires skill, patience, specialized drill bits, and often times, a helper.
Since reproduction fender stays are not always constructed identically to the originals, with slight variances in overall length and tab placement, this is an opportunity for a perfect fit between the existing fender stays and the reproduction undrilled mudguard. Once the location of the holes is established, a spring-loaded center punch is useful for putting an indentation in the mudguard to allow a pilot hole to be drilled. Once the pilot hole is drilled, I’ve found a stepped drill bit works well for gradually working your way up to the desired hole diameter.
At times, even when the utmost of attention to detail is exercised while measuring and drilling, a hole may not quite line up with the fender stay tab. This misalignment requires an adjustment to gain fitment. A simple hand-held tapered and fluted reamer may be up to the task of slightly enlarging the hole. Other times, stretching the hole to a slot is a better choice when I don’t want the hole to be larger.
I call on a cutting drill bit chucked into a power drill for this task. The aggressive teeth on the shank of the cutting bit allow for elongating a hole slightly without increasing the overall diameter. One other tool that is indispensable for fettling is the Dremel rotary tool. This multipurpose tool can be used in many capacities, such as grinding, cutting, shaping, sanding, and polishing. Just select the desired accessory attachment, tighten it in the chuck, and start working. I have a set of rotary deburring bits that are especially useful in cleaning up burrs after cutting and drilling sheet metal.
Pattern Parts And Fettling To Perfection 7Pattern Parts And Fettling To Perfection 8
Some time ago, we had a report from a customer regarding an 83-1571 grab rail, intended for fitment to a 1970 T120R, that was not able to be installed. The alignment seemed to be the problem, and the suspicion was that the part was mis-manufactured and defective. We had a number of these grab rails in stock, so there was concern that we might have a recurrent problem with them as we sold through the remaining stock.
I purchased one for my current project, a 1970 TR6R, although I hadn’t started the tear-down process yet. I wanted to see if I could fit the grab rail to the complete and original motorcycle. After removing the crusty original unit, I set about to install the new reproduction pattern parts. It was a struggle, but I was able to install it without scratching or bending the grab rail, once I loosened up the clip that supports the fender, allowing the fender to move laterally. I wasn’t sure what it was going to take to improve the alignment but figured there was going to be some fettling involved in the final installation, once reassembly of the motorcycle was underway.
Fast forward a year, and the renovation of the TR6R is well underway. The time had come to install the rear mudguard, tail lamp, and grab rail. All of the mounting hardware and brackets were at the ready on the lift. I started by suspending the mudguard with a bungee cord from the rear frame loop while attaching the front lower end of the guard to the previously fitted bracket on the frame. Once the hardware was installed loosely, I fitted the top bridge to the shock mounting bolts, then loosely installed the nuts and bolts from the underside of the mudguard to the bridge. The clip over the rear frame loop was next…also loosely installed.
Now, the moment of truth was upon me, to see just what fun I was in for with the grabrail installation. Indeed, very anti-climactic- it went right on without the slightest need for fettling! I was fully prepared for a battle like I had when I initially tried to install it on the unrestored version of this same motorcycle, with the mounting hardware already tightened. The tail lamp assembly was then easily installed.
The point of this story is that like exhaust systems, grab rails and fenders are best installed with all of the hardware loosely fitted, then the alignment is gained gradually, as you start to nip up the nuts and bolts. There was a little “give and take” while finishing off the rear section, but the adjustments were done without having to drill or grind anything.
‘“If it was easy, everyone would be doing it”’
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Hopefully, the content of this blog is useful in the future when the occasional problem arises during the installation of a non-original part. 9 times out of 10 a part or assembly can be fitted with just a little patience, the correct tools, and some skillful dexterity. As one of my mentors used to say when I started swearing at a disappointing installation event, “If it was easy, everyone would be doing it”. Thanks for taking the time to read this article.
Dave’s photos above are from his 1970 TR6R 10-Foot Project. Check out Part 1 and Part 2 to see how he did it.
