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Air valve on G5 forks

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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan 2019 at 09:21
According to my workshop manual the V50 III and Monza have the oil pneumatic shock absorbers (their description).
Front pressure is 3 kg/sqcm
Rear pressure is 4 kg/sqcm.
Both +/- 1. But both sides must be the same.

Measurement cold and with bike on centre stand.
They also warn that just connecting the guage might be enough to reduce the pressure by a small amount.
Refill with moistureless air.

There is no special damping unit, the air just pressurises the internals of the fork leg.
Brian.

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johnno View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnno Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan 2019 at 11:00
Originally posted by Brian UK Brian UK wrote:

According to my workshop manual the V50 III and Monza have the oil pneumatic shock absorbers (their description).
Front pressure is 3 kg/sqcm
Rear pressure is 4 kg/sqcm.
Both +/- 1. But both sides must be the same.

Measurement cold and with bike on centre stand.
They also warn that just connecting the guage might be enough to reduce the pressure by a small amount.
Refill with moistureless air.

There is no special damping unit, the air just pressurises the internals of the fork leg.
that does work out to be 42psi 
i need to re read the posts

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johnno View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnno Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan 2019 at 11:05
well looks like for the v50 its correct . NOW  what about this G5 lol
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c13pep View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan 2019 at 11:11
I apologise for partially hijacking the thread but I like you (Johnno) am trying to understand the workings of the suspension especially as I have commented before on the stiffness of the forks in particular and whether the air is more important than I had realised. In my case it has prompted me to investigate further with differing pressures when I finally get the Monza up and running

CHRIS
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnno Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan 2019 at 12:59
Originally posted by c13pep c13pep wrote:

I apologise for partially hijacking the thread but I like you (Johnno) am trying to understand the workings of the suspension especially as I have commented before on the stiffness of the forks in particular and whether the air is more important than I had realised. In my case it has prompted me to investigate further with differing pressures when I finally get the Monza up and running

CHRIS
  This thread is interesting 
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FlyingTiger View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FlyingTiger Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jan 2019 at 12:46
Guys - here is a pic
Mark Serj
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TonyF View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TonyF Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jan 2019 at 19:39
Originally posted by TonyF TonyF wrote:



Part of the problem as I recall was keeping the air pressure in the correct range as the specified pressures were small.



I should have said the volumes are small. These days you could use a mountainbike suspension pump to manage the pressures but such things were not around in the day.
Tony
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TonyF Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jan 2019 at 20:00
Originally posted by FlyingTiger FlyingTiger wrote:


Guys - here is a pic



They look like FAC dampers.

Here is a link to a listing on the Gutsibits site:

https://www.gutsibits.co.uk/pr/TheShop/index.php?q=fac+fork+damper&f=d&Model=6&search=SEARCH

The air valves allow you to add a few pounds of air pressure to the fork legs to boost the spring if you wish. You can see the small air hole in the side of the aluminum cartridge top close to where it joins the damper body. There is no air bag in the damper units.


They are probably due for overhaul. I have similar units I bought from Bernie's Spares and Repairs in Watford in the early 80s.

Unscrew the tops and drain the oil. Remove the aluminum spring seat at the bottom and you should see a circlip locating a nylon guide bush and/or the oil seals. There should also be a circlip above the oil seals. Remove these and withdraw the damper assembly. The seals are a standard size. I found the guide bushes had worn so had replacements made. Clean thoroughly and reassemble and refill. I used 10wt shock oil. Put in as much oil as the unit will take while retaining full movement.

Enjoy!

Tony
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FlyingTiger Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jan 2019 at 12:10
Thanks Tony - nice one
 
Regards
Mark Serj
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