Marzocchi Jnr t 2002 tuning

TheCloud

I'm currently running a set of old Jnr Ts on my San Andreas DHS as the more modern 180mm+ dh forks I'd previously tried on it messed up the handling. The steering is fine with these forks, however I can't get them set up right.
Initially they were too stiff and over damped on the rebound which caused them to chatter/pack down mid-travel, so I changed the fork springs to medium (white-genuine Marzocchi), this didn't seem to help much, I then changed the oil to 5wt (140cc each leg), again still too stiff and rebound too slow. I then stripped the forks completely and adjusted the damper holes to half open/closed and changed the oil to a 50:50 mix of 2.5wt and 5wt, again with 140cc in each leg. Now the rebound is a little better, but I'm still not getting anywhere near full travel (90mm tops). I'm about 78kg and quite hard on forks usually, my xc race bike is set up for an 85kg rider on both ends and I acheive full travel on that several times down the same tracks.
The San Andreas has a Fox dhx 5.0 on the back with bottom out adjustment (air piggyback) and pro-pedal. It has occurred to me that this shock is so much better than the forks that stiffness aside, the damping will never feel the same. That said I had some Jnr Ts (2004-5) on my old Specialized Demo 9 a few years ago and they always felt fine, I just can't remember how I had them set up.
Any suggestions welcome.

YeehaaMcgee

To bottom out those forks you're going to need a BIG impact - as with most forks intended for freeride or DH.
The only thing you can do is keep fiddling with the shim stacks.
As far as I recall, there's no external adjustability on those forks?

TheCloud

No there isn't, which is half the trouble really, I think it's certainly a damping issue; if I remember correctly the oil height also has an effect on the damping rate. I had some drop offs with 180mm of travel and used to bottom them out on the same runs, although being air-assist it's hard to compare the two.

YeehaaMcgee

Aye, the oil volume does have an effect. The smaller the air gap at the top of the forks (space between top of oil and top cap) then the more progressive the forks will feel.

nicklouse

Have you downloaded the manual yet?

It will have all the info on the adjustments.

Wat is your weight with kit?
And how much sag are you getting with which springs,oil height?

YeehaaMcgee

Lol, Marzocchi manuals from back then are less than useless - and since there's no external adjustments, it contains zero information about setup, if I remember rightly.

nicklouse

YeehaaMcgee wrote:

Lol, Marzocchi manuals from back then are less than useless - and since there's no external adjustments, it contains zero information about setup, if I remember rightly.

So you have not looked at it then?

It gives full service info. How to set preload and how to adjust the damping.

Actually the better manuals.


OP is it the 150mm version?

And the oil level is a measurement not a volume.

YeehaaMcgee

really? The manual for mine had umpteen pages on how to fit the 20mm axle, crown torque settings, steerer length guidelines, info about default oil height, and er, that was it.
Oh, and a warning about how if I rode it off-road then some Italian guys would put a horse's head in my bed, or words to that effect.

The Northern Monkey

that will be the owners manual out the box and not the workshop manual from the web

YeehaaMcgee

ah.

TheCloud

I had downloaded the manual, and it is pretty useless. I'm about 78kg with riding kit, there's probably only 15-20mm sag when I'm sitting on the bike. I think they're about 140mm travel, probably would reach 150 if maxed out. Just measured the mud marks, only getting 90mm of travel regularly.

Dirtydog11

TheCloud wrote:

there's probably only 15-20mm sag when I'm sitting on the bike.

How much when in attack position?

Re travel

Check your oil levels/volumes!

According to Marzocchis website 2002 Junior Ts should have a 100mm air gap between the top of stanchion and the top of the oil, It's measured with both springs removed and forks fully compressed.

Manual with oil heights here

http://www.marzocchi.com/admin/download.asp?LN=UK&idC=%2D1&Campo=ManualeUnico&IDFolder=126&IDOggetto=2875

TheCloud

I'll give that a try, I've been filling them with springs in, so probably got a bit too much in.

nicklouse

Ok proper 150 mm JrT manual on the way to your email.

TheCloud

Just a courtesy reply for all your help, managed to get the oil levels right and the forks now get full travel, took it for a blast down the new Antur Stiniog black run and they were working as well as can be expected for their age.
Cheers all.