'98 Marzocchi Z2 Atom Bomb help
I recently built up my older Giant frame as a single speed and used a 98 Z2 Atom Bomb to keep the style going, and because it was cheap! It was leaking a bit on the first few rides, so I decided to take it apart, clean it all up and change out the oil and see if that would fix the problem. It seemed to fix the leak but now it feels really stiff, like I am not getting all of the travel out of it. Nowhere near as plush as I would think it should be.
At first, I thought maybe I overfilled the oil on the rebuild, but checking the manual, it seems about right. Anyone got any ideas?
a few pointers on the rebuild
The Z2 atom bomb has an HCSV (I think thats the order of letters) cartridge. When you took the fork apart, did you pump out all the old oil from the cartridge? You definitely need to do this as part of a complete overhaul.
Originally Posted by oldskoolgiant
Next re-assemble the fork with the cartridge in place. Fill with 7 wt fork oil (5 wt if you want quicker action 10 wt if you want slower action)
With the fork top caps off and fork compressed, pump the damping cartridge about 10 times. it should become pretty tough to do with your hands.
Then fill with abit more oil as the cartridge will suck up a good bit of the new oil.
Next cycle the fork (still with the top caps off and the damper carts in the compressed position). This will get the air out from betweent he stanchion and the fork legs.
With the fork and cartridges in the compressed position, fill the fork with oil until the oil level is 30 mm from the top lip of the crown - where the top cap screws in.
That should give you the correct oil level. Now extend the cartridges, put in the springs and attach the top caps with the circlips. Extend the fork, screw on the top caps.
See if that helps. I've gone through about 15- 20 pre 2002 Marz forks. Easy to tear down completely at home with regular tools and the bushing changes are easy and seem to last forever too. Too bad you can't say that anymore.
Very helpful, thanks!
Definitely pumped out all the old oil. I follow you up until you say "cycle to fork". I assume you mean move the stanchions up and down to clear out the air. From there, do you mean that the stanchions should be down when I fill the oil and that the level should be 30mm from the tip of the stanchion in the compressed position? If so, I definitely overfilled. I filled to 37mm from the top of the stanchion in the extended position as the manual states. Tough to tell from the manual if the stanchion is to be compressed or extended though.
The original service manuals of the 97 - 99 forks
Were so much more helpful. Showed how to take the fork apart completely.
Originally Posted by oldskoolgiant
anyway, yes, the crown/stanchion assembly should be pumped up and down. Then leave in compressed/down position to fill the oid AND to fill/pump the dampers.
The oil level should be 30 mm from the lip of the crown - where the top cap screws in to the level of the oil. Use a zip tie, bent at the 30mm length mark as a dip stick.
If you filled the oil to 37 mm with the fork extended, you're WAY over filled. Remember, the air / oil interface in the fork needs to be below the level of the oil seals when all parts are compressed. Otherwise, if the oil is above the oil seal level, you'll be trying to compress the oil as the fork compresses. I believe you'll need a super powerful hydraulic press to do that!!!!
The air in the fork actually acts as a supplimental air spring that ramps up as the fork compresses to help resist bottom out. Pretty simple but effective design. So the less oil you put in (you'll measure greater than 30 mm from the lip of the crown with less oil), the less bottom out resistance, as the air volume increases and the pressure won't 'spike' as fast with compression. if you bottom out too easily, fill it with more oil so it reads less than 30 mm from the lip of the crown. adjust in 2.5 mm increments.