Making a Bobber

Overview

Done properly, a bobber is a motorcycle that has had unnecessary components removed (unnecessary in the opinion of the owner) and is styled to the owner’s taste—no rules. Unfortunately, bobbers can also be badly assembled bitsa bikes that can be dangerous to ride.

There are a number of reasons an owner may wish to make their bike a bobber: a preference for the look/style, lack of replacement parts, accident damage… But whatever the reason, he must be aware of the safety considerations first and foremost.

Removing components from a motorcycle ranges from discarding an unnecessary passenger grab rail (if a solo seat were being used, for example), to removing unused metal brackets from the frame. Regardless of the extent of the modification, each change that takes the bike away from stock must be considered carefully.

A typical bobber will have the following modifications:

  • Front and rear fenders shortened
  • Seat replaced or modified
  • Mufflers replaced or removed
  • Handlebars replaced
  • Custom lights fitted
  • Color scheme change

Fenders

Bobbers typically have shortened fenders. The option here is to either shorten the existing fenders or purchase bobber styled items. 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 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 cut line should be marked with a Sharpie® style fine pen.

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 hack saw 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.

Seats

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 1900s; 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.

Exhaust System

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 the owner does remove the mufflers he should have a professional shop test the carburetor (mixture) settings. As a minimum he should check the spark plug color.

Handlebars

There are many types, styles and designs of motorcycle handlebars. If the owner intends to replace the stock handlebars, he must first carefully examine them to establish the implications. For example, some motorcycles have their switch wiring running through the handlebars. The owner of this type of handlebar assembly must check to see if the switches can be used with external wiring.

(Note: It is not good practice to drill aftermarket handlebars to allow for internal wiring as this can serious affect the structural integrity of the bars).

Besides the electrical switches and wiring considerations connected to handlebar replacement, the owner must also consider the various cables: front brake, clutch and throttle. Cables of differing lengths are available either specifically for a make or model, or as a generic replacement. Before changing the handlebars, the owner should research the aftermarket suppliers to see if cables are available for his particular bike.

Lights

Custom lights are available from many sources: online, motorcycle accessory shops, auto accessory shops etc. However, the owner must ensure that he does not add too many lights with a high amperage requirement as this may discharge the bikes battery. Currently popular, although not historically correct for a bobber, are LED lights. These lights are available in many designs and tend to have a low power requirement.

Color Scheme

Changing the color of a motorcycle's tank, fenders, and side panels is relatively simple. If the owner is not experienced with painting or spraying, or does not have the facilities, a custom shop (car or motorcycle) will generally be happy to perform the work-at a price! It is good practice to seal the inside of the fuel tank before it is sprayed as some of the chemicals used in this process can damage paint.

There are no hard fast rules with the design of a bobber, but the owner must decide early in the process what he/she wishes to achieve. For example, if the owner wishes to personalize his bike and has no intention of selling it later, he is restricted only by his own imagination and the laws relating to motor vehicles where she/he lives. However, the most important consideration must be the safety aspects of the motorcycle.

NOTE:

Modifying a stock motorcycle can have serious safety implications. The owner or rider should seek professional advice before proceeding with any changes to the stock bike.