Marzocchi recommends oil change every 50 hours of intense use and every 100 hours of normal use. If you put some miles in your bike every week, you will reach the first maintenance point very quickly (riding 5 hrs a week, that would be less then 3 months of intense use).

Sending the fork in for oil change makes sense if you have a service center very close, but still represent a significant cost to keep your gear smooth. Marzocchi strongly recommends this operation to be performed by one of their authorized service centers as stated in the Bomber manual on page 113 (version 2005).

I did my first oil change after 12 months (that is about 250 hours of use) and I have to say I did not notice any particular performance degradation at the 1 year mark. If you have a minimum set of mechanical skills and tools this is a relatively simple procedure. Now, here is the DISCLAIMER (read it please):

WARNING:The information contained in this web site describes my experiences tuning and maintaining my suspension forks. This information is not an instruction manual. Use this information at your own risk. I am not in any way responsible for typos, misinformation, or any of your actions or results. Results may vary.

I summarized the procedure in a sequence of steps.

Before you start you will need the following material and tools: – Allen keys (you will need the small ones (2mm)

• Wrench with 21mm socket. A torque wrench is also recommended
• Flat Blade screwdriver
• 7.5wt suspension oil. I used the original Marzocchi, but apparently it is the same as Golden Spectro 125/150 (7.5w) available at your local motorcycle shop
• A flat plastic container or a plate to collect the used oil
• Safety goggles or glasses are always recommended.

1		Remove the red rubber cap from the right side knob and discharge the positive air chamber using the tip of a screwdriver – keep covered with a rug, as some oil may be sprayed outRemove left side knob (TST) using a 2.5mm allen wrench
2		Remove the tiny metal pin, that is used to make the knob clickJust pull it out with your fingers. There is a tiny little spring underneath it. Use a little flat screwdriver or a thin nail to pull the spring out of the hole.
3		Use a small flat screwdriver to remove the C-clip on the TST side
4		Once the little spring is removed, save it in a safe place together with all the other tiny pieces.
5		Remove right side knob (ETA) using a 2mm allen wrench
6		Unscrew right top cap (TST) using using a 21mm socket and ratchet
7		Unscrew left side top cap (ETA) using using a 21mm socket and ratchet
8		Compress the forks enough to expose the cartridges and coils. Prepare some kind of plastic container and pour the oil in it.
9		This is how forks oil looked after 12 months of use. The oil in the TST side was pretty clear. The oil from TAS/ETA side was dark and smelly. Leave the forks upside down for a little while and let all the oil drain.
10		Remove bottom side knobs (TAS and Rebound) using a Xmas allen wrench. Be careful and save all the itty bitty parts in a plastic bin or box.
11		Unscrew footnuts on both sides using a 12mm spanner. some more oil will come out so be prepared to catch it.
12		Remove cartridges and drain all oil you can.
13		You can cycle the coil cartridge a few times to let all the oil out. In order to do so it is recommended to remove the top cap from the cartridge and remove the coil. This will also make it easier to cycle the same cartridge when will add back oil. I also recommend to leave the TST cartridge alone. Last time I decided to cycle it some air found its way into the cartridge and I had to take a trip to Marzocchi to have it purged. Leave the TST alone, just clean it but don’t cycle the rod.
14		Separate uppers from lowers carefully. Clean everything with paper towel or with a lint free rag. Old T-shirts are ideal for this kind of task.
15		Smear a touch of a light grease (Rock N’ Roll’s Super Slick Grease – $6.49 a tube) on the seals and on the stachions. Don’t put too much. Too much grease will contaminate the oil. Parts that need to be lubed are already in contact with the fork’s oil. This picture here already shows a little too much grease on.
16		Put back uppers into lowers. Be careful, try them to go evenly in. Put cartridges in
17		Tighten Footnuts to specified torque
18		With the uppers all the way into the lowers, add oil until you have only like 50mm from the top of the stanchion to the surface of oil. Cycle the rods to ensure you don’t have any air in the cartridges, otherwise your oil height will drop and the ETA will not work.
19		CAREFULLY, put top caps and tighten them up. Be careful to avoid cross threading. You should be able to screw in the top caps almost all the way with your bare hands.
20		Put knobs back on. Reassemble all the little tiny parts for the ETA and TST knobs.
21		You are done. Test the forks compressing it manually, making sure everything works and there are no leaks.It will take a little while for the forks to adjust. Ride it on your driveway a few times before taking her back to the trail.

MORE INFO

You can find detailed instructions on how to change oil in Marathon S 03 on this site.
You can find another good source of information on various forks on the Enduro Fork Seals web site

The video below shows how to bleed the TST cartdrige in case you need to do that.