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Marzocchi 50 CC (twin chamber) rebuild

B

Bart

Husqvarna
AA Class
So I'm rebuilding/servicing my friends Marzocchi 50mm twin chamber forks.

Is it important what weight oil is in the outer chamber, I don't see how a different oil would change the action in the outer tube, it doesn't have any valves in it. What is the preferred oil amount, for MX riding (does 310cc sound alright?).
 
What bike?

I think the manual says ~320 CCs for each side if my memory is correct ... The most I have run is 280cc and that was too much for trails so I dropped to 240cc...

For MX stuff, not really sure because the valving plays so much of a role here ... Is the shim stack stock? My stack has a few changes and I weight about 155lbs in gear, not too big a jumper, and would not go past 290cc as a starting point ... Adding fluid past 280cc seemed to really stiffen the forks up on my 08 TXC250 forks greatly ...

Also, how will the bike jump on the tracks?

As far as weight, the WT might matter to a small degree but not alot from what I was trying a couple yrs back ... I just run ATF fluid there now ...

Trial and error might be the answer you are looking for from a known starting point ...
 
There is a special bleed process for the inner chamber... Jmetteer did a write up if I remember right, explaining the special tool needed (can make one out of pvc), and the bleeding process.
 
Blakelpd5 said:
There is a special bleed process for the inner chamber... Jmetteer did a write up if I remember right, explaining the special tool needed (can make one out of pvc), and the bleeding process.
Click to expand...

And Jmetteer is a jumper :) ... He should have an idea of what the oil levels are all about ...
 
Finished the rebuilt Monday.
Put 300cc 10wt (and a bit 7,5wt cause it was all I had) per leg in.
The bleeding procedure wasn't that pleasant, messy with allot of oil spillage, the air is all out.
Couldn't manage to preload/preexpand the bladder, how much expanded should it really be?
 
Did you get the tool (or make it) to clamp around the top of the bladder? I don't remember the exact procedure off hand, but it's imperative that it is used. You should for sure be able to see the bladder expand when you push the rod in. If not, I'd suspect you don't have the proper amount of oil in there, even if it is bled below the piston.
 
Yes I made a collar of PVC.
When fully compressed, the bladder expanded quite a bit, but when fully extended there weren't any dimples.
 
Bart said:
Finished the rebuilt Monday.
Put 300cc 10wt (and a bit 7,5wt cause it was all I had) per leg in.
The bleeding procedure wasn't that pleasant, messy with allot of oil spillage, the air is all out.
Couldn't manage to preload/preexpand the bladder, how much expanded should it really be?
Click to expand...

How did this tuning work out on the track?
 
Not sure, haven't had the time to test it, all tracks in my region are closed at this time (Belgium, The Netherlands), due to snow and bad weather.
Mind you this is for a TM Racing, so valving might be different.
MXA did a write up of the TM 250 and 300 and there's a suspension setup they liked the most (could be helpful).
 
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