Gregory Bender

Transmission leaks - four speed layshaft (output shaft)

Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models


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The four speed transmission layshaft (output shaft) is sealed using a typical oil seal. The oil seal is pressed into the rear cover of the transmission and seals against the outside diameter of a metal ring that slides onto the output shaft. In front of the metal ring is the speedometer worm drive gear, then a shimming washer, then the rear bearing for the layshaft (output shaft). There is no means (other than by metal-to-metal contact) by which to prevent gear oil from escaping from between the layshaft (output shaft) and the metal ring. To further complicate matters, there is a square key-way that runs the from the rear of the layshaft up to the bearing.

If the matting surfaces of all the components are in perfect condition, the 150 foot pounds of torque required to secure the ring nut would probably be sufficient to prevent oil from escaping. But if the surfaces are less than perfect - as is typical of 35 year old parts - problems can arise.

It would seem that a 2-pronged approach would alleviate this problem:

  1. Mill a small recess on one end of the metal ring to accept an o-ring. The O-ring will compress against the speedometer worm-drive gear.
  2. Fit a slightly-oversized square O-ring into the square key-way, compressing it in place with the metal ring.

I have not attempted this modification.