Gregory Bender

Generator pulley fitment

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


// //

It seems such a simple thing to fit the generator drive pulley to the crankshaft. Sadly, all too often they are fit incorrectly. The results range from annoying (inability to properly time the ignition) to destructive (ruined pulleys, broken generator brackets, destroyed timing chest covers). Here are the basic instructions:

  1. Rotate the crankshaft until the left cylinder is at top dead center.
  2. Place the pulley half with the notch(es) onto the crankshaft.
    • The notch(es) should point toward the left cylinder (which is now at top dead center).
    • There are only three positions in which the pulley can be placed, so if the notch(es) do not point upward toward the left cylinder, just try each position until they do.
  3. Place 1 - 5 spacers to adjust the belt tension. Start with 5 spacers and reduce that number as necessary to achieve proper tension (see below).
  4. Place the pulley half without the notches onto the crankshaft.
  5. Place any remaining spacers onto the crankshaft (in front of the front pulley half). Yes, all 5 spacers must be installed at all times, either in-between the pulley halves or in front of the front pulley half.
  6. Fit bolts with lock not tighten at this time, just start the threads.
    • If you fit bolts longer than 16 mm, they will dig into and distort the timing chest cover, make a horrible grinding noise, etc.
    • Tip from Charlie Mullendore of Antietam Classic Cycle:

      Here's a tip I've used for years - cut the head off of a 6 mm bolt approximately 40 mm long and screw that into one of the pulley hub holes as an aligning pin for the pulley halves and shims. Makes assembly just a bit easier.

  7. Fit belt to pulley.
  8. Tighten bolts just a little bit. If you tighten too much, you will bend/crack/break the pulley.
  9. Rotate the crankshaft at least 360°. This encourages the belt to ride up onto the pulley. This step is critical.
  10. Repeat steps 8 and 9 (incrementally tightening the bolts after rotating the crankshaft) until the bolts are fully tight.
  11. Check the tension on your belt. It should feel loose, not tight. One of the biggest causes of broken generator brackets and the studs that secure the bracket to the crankcase is overtightening the belt. You should very intentionally keep the belt on the loose side. Belts are much easier to replace than repairing a broken generator bracket.