Now FAC damper issue, I think

[amamet]

so I decided to completely disassembly my forks from my lemans I.  took the progressive springs off the fac damper just to do it since I never had before.  what I noticed is that 1 damper when the rod is compressed to the body it stays compressed where the other slowly extends out about 5".   what's going on here?  any help would be appreciated
thx
allen

[Antietam Classic Cycle]

One has residual air pressure in it and the other doesn't?

[amamet]

what should it be doing?  staying compressed or extending?  I don't really know.  im pretty new at fork internals...but learning

[lucian]

I replaced the oem air dampers with bitubo non adjustable ones from harpers on a LMIII what a great improvement, no more front end dive under braking and huge improvement on Maines bumpy roads. As far as your springs I don't think it would actually matter that much if one were opposed but mine were installed with both tight coils up . Also  if one has some air pressure it will tend to push itself out but more importantly you should not be able to pull one in and out without resistance. clamp on end in a padded vise and push and pull until your mad, if you can have your way with either of them it's toast.

[amamet]

well, I can hold the body of the damper and push and pull the rod in and out

[amamet]

https://youtu.be/k57-9QAd7zc
https://youtu.be/0BMt2_IawBI

here's 2 videos of me being able to push and pull the damper rod. its pretty easy to compress and extend each rod.

[lucian]

It should resist both directions, the faster you push or pull the more it should resist. If it just pulls in and out with ease the internal seals are gone . they can be rebuilt but for the time and parts it's just as cost effective to replace them.

[amamet]

hmm, they pull out with some resistance but collapse pretty easily

[lucian]

Those are toast ,  should be more like trying to pull a screen door closer if you follow me, you'll definitely see a huge improvement in front end feel if you upgrade those.

[Antietam Classic Cycle]

They should be held upright (in the same position as when they're installed) when testing. FACs have less compression damping than they do rebound damping, so the rod will go in easier than it extends.

If you'd like to try rebuilding them, here's some information that might help:
http://thisoldtractor.com/moto_guzzi_tonti_fac_damper_rebuild_information.html

[amamet]

I took the caps off to look inside, what I noticed was that one had about 1/2' less oil than the other.  what kind of oil is in there and how much?  is there a manual for these dampers anywhere?  I can't seem to find any literature online. the bike came to me like this

[amamet]

still curious as to why one extends by itself.  if there was residual air inside, shouldn't that have "escaped" when I took the top cap off?

[lucian]

According to the rebuild post Charlie provided it calls for 70ml. of 10w fork oil per side, My guess is that the one that extends itself has a working compression seal and a leaking rebound seal so when it's compressed it builds pressure but has no resistance to return to full extension.

here's an interesting read on the subject, perhaps air has leaked by the compression seal and is causing the spring back.

https://racetech.com/html_files/DampingRodForks.HTML

[Stevex]

As Charlie says, they need to be upright before you compress them, there is an air gap in them and you can hear the air going through the restrictor piston with them horizontal. The compression damping will be less than the rebound damping as the spring does a lot of the compression damping. The rebound damping has to cope with the spring extending and prevent you pogo-ing down the road. I don't see a problem with your dampers.
Try them up right, I'm sure they'll be OK.