MX Pro w/ETA Oil height procedure
It appears that many owners of MX Pros with ETA do not get the full travel of their fork. Various opinions on the cause and possible solutions have appeared on the web. The predominate opinion is that excessive oil is at the heart of the problem, but there is a lot of conflicting info on appropriate oil levels and procedures for measuring the levels.
After some thought and a lot of trial and error I believe the following procedure will enable maximum travel while also setting the oil level as high as possible without limiting the travel. It seems to me that this should be quite safe for the fork. Note: I am in no way a Marzocchi expert and these procedures are only my own. They work for me. but use at your own risk. My fork is a 2003.
Procedure:
(I find it easiest to do the following with the bike upright and on it's wheels. I mount the back end in a trainer to hold the bike up while I work the front end.)
1. Release the air from the right leg through the fill valve.
2. Remove the right leg air chamber cap. You should be able to look down in and see oil at this point.
3. Remove the allen screw holding the ETA lever on top of the left leg and remove the lever.
4. Remove the left leg cap. The coil spring will move up and part way out of the leg and the fork will completely compress. At this point you can cycle the fork all the way out and back to confirm that the full potential travel is possible. Note that some of the total travel is negative travel. So first pull the fork to full extension, then allow it to compress fully to see the full travel. With my model (2003) I get 5 mm negative plus 80 mm positive or 85 mm total travel.
5. Experimentation has shown that setting the right leg oil to 10 mm below the top of the fork tube allowed full travel. This can be tested by putting the right cap back on and pushing down hard on the handlebars to ensure you still get full travel (the left leg spring is still released for this).
Too much oil and you won't get full travel. I don't know all the consequences of too little oil, but by putting in the most that will allow full travel, it seems safe. Also, Marz specs 10 mm, so this is probably correct. Many have advised reducing this to 50 mm, which just seems unnecessary to me. Small additions make a significant difference. I tweeked the level a little around the 10 mm level (mm or so) so the fork stops just before hitting the hard end of travel and making a clunk sound, so I may have given up a mm of travel.
The most important part of this step is to measure the 10 mm from the top of the oil to the top of the fork tube (not the crown) The tube ends inside the crown and has internal threads to the top end. In my model it has a goldish color.
Leave the cap off for now, and move on to the left leg.
6. Because of the spring, the left leg oil height is hard to measure. Instead, I used the same principle of putting the most oil in that will allow full travel. The fork should still be in its fully compressed position. First carefully push the spring back down into the fork leg with you hand. This is fairly easy if you put a socket over the cap nut to push on. Push it all the way to the point where you could begin to screw in the cap, but don't screw it in. Be careful not to damage the o-ring in the cap. If oil overflows out of the leg, then there was too much in there to allow full travel. ( I suggest covering your disk caliper with a rag to prevent getting oil on the pads.) If there is no overflow, it is not overfilled, but could be underfilled. Add small amount of oil to the left leg and try again. Repeat this until you get some overflow when the spring is fully compressed into the leg. I think this is the maximum amount that will allow full travel.
7. Put both caps on.
8. Replace the ETA lever.
That's it! You should now be able to push down on the bars and/or jump on the pedals and see full travel for perhaps the first time! That's what happened with mine. Sweet!
9. Add air to the right leg to set your desired sag. For my weight (145 lb) and riding style, that was about 30 psi to get around 20% of full travel as sag.
Good luck.
