Apparently the alignment of the rear drive pulleys can make the drive belt not run centrally. This can be corrected by performing the simple modification submitted to us by John Russell in 2001.
Shown right is a drawing of the two speed shaft (part number 901610) with the brake/pulley adapter (part number 9614) in place.
The square driving peg on the two speed shaft does not sit into the bottom of the machined slot in the brake/pulley adapter as it is round and therefore holds the pulley off to one side.
It is relatively straightforward to file the bottom of the slot in the brake/pulley adapter so that it is located further across the shaft.
The pulley will then be in the right place to line up with the rear axle pulley (part number 909372). Be careful to only remove enough metal in order to line up the pulleys, or you will create more problems for yourself.
Many thanks to John Russell for submitting this tip.
For further information regarding the rest of the Serpent range of model cars and accessories please visit the Serpent web site.