Well, Bugger me, it's started doing this again - and worse...
Came out to the bike yesterday morning, and a there was a large 'dent' in the tank. I was PISSED
However, opening the gas cap released a lot of vacuum, and the dent pretty much went away. I didn't know painted plastic was that flexible...
Anyway, I obviously have a venting issue. Something (crankcase vacuum after shutdown, temperature changes ??) is generating a strong vacuum.
I removed the gas cap completely, and blew thru the 2 vents both ways and they were clear.
I suspect the problem is with this contraption inside the filler neck:[You must be registered and logged in to see this link.]
So, has anyone worked-on or had issues with this ??
(For the ever helpful Aussie Gurus - you may not have this thing. My bike is a US-spec 2008 1100, and this looks like some emissions-related crap)
This part of the filler neck covers the vent tube (I think) under this cover is a ball check-valve. I think its to allow over-pressure venting, but not spill in a tip--over ?
The Moto Guzzi Workshop Manual and Parts List is, as always, f-ing useless. It shows the tank cap as one complete unassembled item.
The Guzzi Engineers really should invite the Technical Writers to the pasta lunches where all this stuff is designed and discussed. Then they'll know WTF some of the parts on the bike actually do....