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INSTALLING #192065010010 TRANSMISSION BREATHER
The only thing worse than the fact that Moto Guzzi 500 and 650 small-twin transmissions blow gear lube out their vents is that the external ribbing of the transmission case holds it there in a deep, gooey puddle.
For models after 1981 Moto Guzzi called for 900cc of gear lube rather than 1000cc in an attempt to limit the problem. Later bikes also have plastic shrouds around the transmission gears to limit the amount of gear lube thrown off. We have never seen a service notice that authorizes using the reduced amount of gear lube in earlier bikes. Since we view the quantity reduction as only an attempt to solve the vent problem, we recommend that the full 1000cc measure be used in all small twin transmission and that the vent problem be dealt with in a way that doesn’t have the potential to cause more serious internal problems. Guzzi must have agreed, as more recent models again call for 1000cc.
In the late ’80s Guzzi relocated the level/fill hole on the transmission for the reduced lube quantity. No U.S. bikes came with this update although a replacement transmission case may include this change.
The new breather cap supplied in this kit directly replaces the original and will preload the shift detent spring under it the same amount as long as you use the standard aluminum sealing washer, as provided in the kit.
The biggest installation problem is gaining access to the breather cap, which varies with the model bike and the type of air cleaners. You may find it easier to remove the right-hand carburetor than to fight it.
There is nothing magical about the new cap; it can’t do anything more to keep the gear lube in the transmission than the original did. We figure if you can’t beat a problem at least contain it and that’s the idea here. With the new cap in place, install the hose so that it looks like a 4” tall upside-down “U” and secure it to the cap with a nylon tie. Use another tie to secure the outlet end of the hose to the cap making sure not to pinch the hose closed at the top of the “U”. Use a final nylon tie if necessary to secure the upper part of the hose. This arrangement allows the transmission to breath while returning expelled gear lube which can’t climb past the bend in the hose. It’s not perfect and it certainly is ugly, but it works much better than the original arrangement.
CHS 2065