Gregory Bender

Transmission - Shimming the shift drum

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

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Shim the shift drum

This sounded scary and difficult to me at first, but it turned out very easy to do (especially with some help from John Ulrich on a cold Minnesota Saturday at the end of January, 2004). And the results are great: fewer false neutrals, reduced clunking when shifting, less shift pedal movement required to engage gears, etc.

Thinking - Myself and John Ulrich
Thinking - Myself and John Ulrich

Photo courtesy of Angela Bender.

More thinking - Myself and John Ulrich
More thinking - Myself and John Ulrich

Photo courtesy of Angela Bender.

Horsing around - John Ulrich and myself
Horsing around - John Ulrich and myself

Photo courtesy of Angela Bender.

Finally a little work gets done - John turns the clutch input hub while I shift through the gears
Finally a little work gets done - John turns the clutch input hub while I shift through the gears

Photo courtesy of Angela Bender.

For materials, you'll just need a supply of shims...they come in the following sizes: 0.6 mm (MG# 55235000), 0.8 mm (MG# 55235001), 1 mm (MG# 55235002), and 1.2 mm (MG# 55235003). The shims are cheap, so I got two of each and now have plenty of extras. The outside diameter of the shims is 22 mm and the inside diameter is 8 mm. But none of these dimensions are critical. A selection of inch shims with an inside diameter of 516 inch and an outside diameter of 34 inch, 78 inch, or 1 inch would work well, too (using thicknesses of 0.02 inch, 0.03 inch, 0.04 inch, and 0.05 inch).

Check the shift forks for excessive wear

I'm not aware of any exact specs for how much wear is acceptable. Replacing them is not cheap. They run about USD $100.00 a piece - which is a lot of money considering that you might be able to pick up an entire used 4 speed transmission off of eBay for less than USD $100.00 delivered. Keep track of the relative position of each fork as you remove them. You'll want to check for wear patterns against the associated gear. My forks only had slight wear, so I reused them.

Special tools you will need

  1. Generic gear puller to remove the clutch hub from the clutch shaft (this isn't so special a tool, but I thought I should mention it anyway)
  2. For 5 speed transmissions, a special ring nut is used to secure the clutch hub. A special socket is required to remove it.
  3. Special socket/wrench to remove the lock ring from the layshaft (the 4 speed and 5 speed transmissions have different nuts, so a unique special tool is required for each.)
  4. Some type of wrench (perhaps a large pipe wrench, perhaps a special tool) for holding either the layshaft or the clutch hub while tightening the lock ring on the layshaft.