Go to any well-equipped motorcycle workshop and you will see a hydraulic press. The reason for this is simple: to do certain mechanical jobs on motorcycles, a press is essential. 

As a mechanic’s tool box expands, so too does his or her range of jobs that can be tackled. A mechanic may repair set of bent forks by simply replacing them. But with experience and more specialized tools, he could easily straighten the damaged legs—possibly offering this service to other shops.

 

Types of Presses

There are a number of different types of presses, but all offer the same basic function: to apply a load to a specific area. Early examples of presses (still seen in some motorcycle dealership workshops) were based on the screw press (or fly press) principle where a threaded shaft was screwed down onto a work piece, thereby adding pressure to a given area. The fly press design involves a large weighted handle on top of a threaded bar which was spun around by the operator to increase the pressure on the work piece. The momentum of the handle introduced kinetic energy onto the regular screw press’s pressure.  

By far the most popular press used in motorcycle workshops is the hydraulic press. These presses (typically offering pressures from 10 to 20 tons) are relatively inexpensive. Prices range from around $200 for the hand-operated type, to $5,000 for the electric/hydraulic types. 

Press Uses

Although somewhat limited in the range of jobs that an hydraulic press can be used for, they are invaluable for:

• Pressing out bearings or seals
• Rebuilding 2-stroke crankshafts
• Straightening lightly bent fork legs
• Pressing in/out bushes

A Worked Example

As mentioned, one job on motorcycles that an hydraulic press is very useful for is to straighten a set of bent fork legs. The mechanic will have removed the forks and fully disassembled them in readiness for the straightening procedure.

The first part of the straightening process is to determine where the legs are bent, and to what extent. This is best done by placing the legs in a set of ‘V’ blocks or knife edge rollers with a dial gauge to measure the amount of deflection. The high point on the leg should be marked with a dry erase marker--this is the point at which the press will apply pressure. (See note one below regarding using lathes.) 

With the high point marked on the fork leg, the leg should be placed into the press on a set of ‘V’ blocks. The actual pressure point in the press should have a cupped (half round) aluminum piece to apply pressure to the leg. The operator will find that the fork leg must be bent slightly beyond straight as the leg will have a certain amount of spring-back. This process will need to be repeated a number of times to get the leg back to straight. 

Once the fork leg is straight again, it should be polished with medium grade Scotch-Brite™. 

Notes:

1) A more accurate method of determining the location of a bend in a set of fork legs is to place the leg in a lathe and support it at both ends. A dry erase marker should be clamped in the cross feed and brought to bear on the fork leg as the mechanic revolves the chuck by hand. By moving the marker along the fork leg, a mark will appear at the beginning and end of the bend. The center of this mark represents the exact position where the hydraulic press should bring pressure to bear. 

2) Of the utmost importance when using an hydraulic press is safety. Operators must wear safety glasses at all times and ensure that the work piece is securely fastened before applying pressure (see three below).

3) The tooling used on hydraulic presses must be in good condition (safety). Ideally, the operator will use aluminum blocks to apply pressure. Note: Round aluminum pieces should be periodically machined in a lathe to ensure a flat surface.