The entire look and optimum performances of the chopper motorcycles are distinctly different from the factory motorcycles. Bobber motorcycles usually consist of a stripped stock motorcycle, shortened fender, and other essential parts and accessories that can be seen in other motorcycles. One main thing that clearly differentiates between a bobber and a chopper is that bobbers keep the original factory bike while in contrast to a modification of a factory frame.
In terms of appearance, bobber motorcycles are much more lightweight and minimalistic with less chrome when compared to a chopper. The origin of bobber motorcycles could be traced back to the time when servicemen were returning home from war, and they began to remove some parts of their bikes that were not really crucial to the basic functioning of the motorcycle. Some of these parts include front brakes, indicators, and more.
There you have it! Perhaps a succinct explanation of the differences between a bobber and a chopper. There are many companies advertising bobber style fenders on the web, but the buyer must research both the item and company before purchasing. Modifying an existing fender is a relatively simple engineering job, requiring few tools.
However, if the motorcycle being modified to bobber style is a rare example, the owner should consider keeping the original parts as this may add considerable value when selling the bike in the future. Alternatively, the stock fenders can be sold and the money put towards purpose-built items.
Assuming the original fender is made from steel, the first part of modifying them is to decide on the cut point. Each owner will have their own idea as to the length he wants his fenders to be, however, he should consider leaving a little extra metal to allow for having the edges rolled by a professional sheet metal shop. The original bobbers would generally have their fenders sawn off and the rough edge left as cut. Besides the obvious danger aspects of this type of finish, having sharp edges on a fender is illegal in most countries-best to check before cutting see note.
There are a number of options for cutting steel fenders. A regular hacksaw with a fine tooth blade 32 TPI is the cheapest way of cutting the fender, but will predominantly cut in a straight line. A number of cuts may be necessary, therefore, to obtain a radiused finish. An electrically powered jigsaw cutter can also be used to cut a fender. However, when using a jigsaw cutter, it is good practice to apply masking tape towards the inside of the cut line on the portion of the fender that will be kept as jigsaw cutters tend to leave a scraped line where they were pressed against the metal.
The finish of the fender is down to the owner's choice; however, the bare metal edge produced by the cutting process will inevitably rust. Therefore, it is important to apply paint to the edge as a minimum.
Alternatively, the fender can be re- chromed , powder coated or fully painted. The seat on a bobber is an area where many owners like to express their personal preference. Traditionally, bobber seats where a single seat resembling the board track racers of the early s; modifying an existing seat to look like one of these is early board track seats is difficult. The problem lies in the design and construction of modern seats.
The majority of motorcycle seats have a pressed steel base, these bases have ribs and pressings in them to make the relatively thin steel stronger. If the seat is cut from a dual seat to a single seat unit, some of the torsional strength will be lost. In addition, many double seats have their locating brackets in the front and rear. If the rear section is removed, new rear mounting brackets must obviously be fabricated.
Purpose built bobber style seats are available but the owner must decide if he considers the price worthwhile. Removing the mufflers was a typical bobber modification. However, increasing the sound levels of a stock motorcycle is illegal in many US states and various countries.
In addition, removing mufflers will have an effect on the engine's running condition, generally having the effect of leaning out the mixture. A lean running engine can lead to overheating and serious internal damage. If you are reusing your stock wheels you may be simply using tires to fit these existing wheels.
Once you have decided on which tires you are going to use you can move on to the fenders. As we mentioned earlier, many bobbers have no front fender at all. However, running a small smooth or ribbed front fender can be true to the bobber style and can be quite useful especially when riding in the rain! There are many styles of rear fenders available, in multiple different widths. Here are just a few rear fender options out of the many that can be used to make your bobber stand out from the rest.
Top left: A stock vintage fender. Bottom left: A Gasbox Steel 16" fender for vintage tires. It is very important to have proper tire-to-fender clearance when mounting your fenders. If you choose to run a modern-style tire and later switch to a higher-sidewall, vintage styled tire, you may have issues with the tire simply not fitting under your fender, or rubbing as it expands at high speeds.
You can see the hose on the rear tire on Todd's Triumph bobber project to help with the spacing of the rear fender. This helps set the distance between the tire and the fender. One trick for mounting your fender is to tape a piece of old motorcycle drive chain, or a piece of garden hose or tubing, around the circumference of your tire where the fender will sit. You can set your fender on top of this chain or tubing, which will act as the clearance between your fender and tire.
You can now fabricate the fender mounts from your frame to fender, and your fender struts that support the end of the fender, without worrying about the fender being too close to the tire tread. A variety of weld-on fender mounts and fender strut kits are available to help the professional or home-builder alike. Another important part to consider is the oil tank. This means that the oil is stored in the engine itself as opposed to a separate, stand-alone oil tank.
Some builders will make a dummy oil tank on a wet sump bike, such as a Yamaha XS, as it is a convenient place to house any electronics or the battery. In many cases the stock oil tank on a dry sump bike can still be used on a bobber build.
Depending on the changes made to the frame you may be able to use the stock oil tank. If not, a popular choice is a cylindrical oil tank, which are available in a variety of styles, including domed or dimpled ends.
These custom bobber oil tanks will need to have mounts welded to your frame, but are otherwise very straight-forward to install. Hose fittings allow oil lines to be run to the engine and back with ease. When mounting a custom oil tank be sure to make three mounting points. Less than this tends to lead to failure and broken mounts over time, and having the oil tank mounts crack on your bike is a great way to cause you some trouble on the weekend!
Rubber mounting your oil tank is an excellent way to isolate the oil tank from vibration, which protects the tank and mounts from cracking, and also keeps the oil from frothing or coming out of your breather vent. Different weld-on rubber mount tabs are available that make this a popular option. Motorcycle seats come in many variations and styles, but there are a couple of differentiators to separate some of the styles.
Rigid mount seats would be any motorcycle seat that mounts to the frame and does not offer any sort of support. These seats are available as solo seats, in that it is just for the rider of the bike, and two-up seats, which also allow for a passenger.
Sprung seats are commonly called solo seats as well, but traditionally use springs between the rear of the seat and the frame, and a solo seat pivot at the front of the seat to allow it to pivot. This gives the rider some suspension to absorb the bumps and vibration from the road. Original bobbers typically had a solo seat, which was often a larger saddle seat with a stock seat post.
The seat support post slides into the stock frame and uses springs and bushings to give suspension to the rider and soften the ride. These types of seats are found on vintage Harley-Davidsons from early models like the Knucklehead and Panhead on up through Shovelheads. Smaller sprung seats made their appearance on customized bikes and early choppers, lowering the seating position of the rider. A sprung solo seat can easily be fitted to any hardtailed motorcycle.
In addition to the seat itself, a solo seat pivot, a set of weld-on or bolt-on solo seat spring mounts and some seat springs are needed to complete the installation. Finally, the cost is something to consider, both for the base motorcycle as well as for various parts necessary for the build. As with any complex or large project, it is helpful to decide how much time and money you are going to spend on your project.
Having an overall idea of the money you have available will help determine what the starting bike will be, as well as other elements, such as whether you will have a professional paint job and chrome plating or aim to keep stock finishes or paint the bike yourself. One way you keep your budget in check for a bobber build is by starting with a quality motorcycle to begin with. While it may seem like a good idea to buy an engine or a frame and piece the rest together bit-by-bit, this can often end up costing more money, as well as time, in the end.
Getting a running, riding motorcycle will eliminate many potential expensive hassles during your build. Your budget may also dictate if you are doing all the work yourself versus finding a professional to help with mechanical or fabrication on your build. The finish work, that is, polish, painting and plating, can often be a large part of the expense of building a bobber. If you are on a tight budget consider high temp painting or ceramic coating an exhaust instead of chrome plating it, learning to paint your tank and fenders yourself, and going with materials for handmade parts such as aluminum or stainless steel.
These can be sanded and finished with scotchbrite or buffed to a shine on your own buffing wheel instead of having to be plated at a higher cost. Building a custom motorcycle and then getting to ride it down the road can be extremely satisfying and give a real sense of accomplishment. In my personal experience, the time spent riding a motorcycle I built with my own hands is greatly enhanced because I know that machine inside and out.
Motorcycling offers such room for growth in terms of mechanical and fabrication knowledge that it is almost endless.
It is a pursuit that pays dividends in many areas of life, as the knowledge carries over to so many other activities. And of course, being able to take the vision that exists in your head and make it a reality is fulfilling. A stock, early 's Yamaha XS motorcycle, which is a great option as a starting point to build a bobber motorcycle. A custom Yamaha XS chopper, quite the difference from the stock motorcycle pictured just above! Photo by: David Carlo. Here's another one of Todd's vintage Triumph bobber builds.
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