Models 308 / 358 / 408/508
By Bill Arp

The question concerns the replacement of bail springs for the ultra-lite Mitchell’s. Given this task, I did some research and found some interesting facts that I am quite sure will be beneficial to all interested parties. For many years, users of these models often changed the bail springs only to encounter problems with proper fit-up. Unknown at the time was that Mitchell made a design change to the bail spring that is not compatible with older versions. Mitchell made two different size bail springs during the years of manufacturing these models.  The original bail spring had a four-coil design and the newer issue, has five coils. Each of these springs is not interchangeable except with the addition of a special collar.

When Mitchell first introduced the original 308, 408, 508 & 358 during the early 1960s, it was designed with a small length boss (the bail spring recess area) on the rotor cup.  The spring for the early version of these models was a shorter four-coil design that Mitchell decided to modify with a longer 5 coil spring design

The original spring for the models, 308, 408, 508 and 358 is part number 81287.  In contrast, left hand versions, 309 and 409 use part number, 81288.  Before changing the spring for either version, it is necessary to identify the reel’s serial number that can be located under the reel foot. Early models having a serial number below 560650 are fitted with a four-coil spring.  Those reels have a serial number of 560651 or higher, use the five-coil bail spring.

The five-coil spring offers better performance but cannot be utilized on reels that are designed for the shorter four-coil spring. Reels having the serial number 702331 and higher have a number 5 stamped on the underside of the rotating head.  This lets you identify that a five-coil bail spring is needed. Between serial numbers, 560651 and 702331, it was assumed.

Mitchell, in March 1975, modified the boss length to make it higher.  If you have the earlier four-coil version model and would like to use the five-coil spring, this can be accomplished by removing the metal collar ring (Part #35078) over the boss to increase the height to fit the longer spring.