Selector shaft oil leak

[Pancake]

Evening All,

I have a query about a persistent leak from the selector shaft on the gearbox. I have bought an O ring for it but in all the descriptions and exploded diagrams I've seen, there doesn't appear to any mention of this O ring.
I have the off and now all I have to to is to get the back off the gearbox, which is easier said than done. I tried spragging like in the Haynes manual, but that didn't work at all.

Any ideas about this O ring? Has anyone else experienced a selector shaft leak? It's only been bugging me for 20 years and finally I'm ready to do something about it!

By the way the bike is a Spada 2

[Kiwi_Roy]

The nearest I have seen was an old loop, it didn't have an "O" ring
Won't hurt to try though.

[Antietam Classic Cycle]

All 5 spd. "big block" transmissions have an o-ring on the selector shaft. Like any o-ring, they can become hard and brittle with age, then leak. 

[acogoff]

     Yes, Pancake, the rear cover has to come off and the gear selector shaft has to be removed from the inside. I would not even attempt it unless transmission is on the bench in the vertical position. Have you considered that the transmission is being over filled causing the excess to find a way out? 750cc and no more is the fill amount on a Tonti 5 speeds.

[Wayne Orwig]

Yep, cover has to come off. The o-ring rides in a groove inside the hole, once you pull the shift shaft out.
Also make sure you simply do not have the fluid level way too high.

I had a Guzzi leak VERY badly there, when new. They replaced the o-ring and it still leaked badly. Turns out the cover had a defect and had to be replaced. Never seen a drop any other time.

[Pancake]

Thanks for the helpful replies. I'm pretty sure it hasn't been overfilled over the 20 years I've had the bike, but perhaps it has even though I have been rigorous in putting in only 750cc, or at least I think I have, it's been a while since I last changed the oil!

I've just taken it to a local garage to get the output nut rattled off so I can remove the the end of the gearbox.

We shall see...