I bought a 93/94 Giant ATX 770 bike yesterday for $50. It came with DX hubs, front derailleur and canits. it also came with an old Trek Mogul air fork.

I like projects, so I bought this one to rebuild it with some of the original components and some I have lying around, just something to keep my hands busy.

About the fork. It does hold air, at lease for 24 hours, but I have no clue when it comes to air/oil shocks. I could look around the net but I have no idea if these shocks are similar to others and if the info would be helpful.

What can I do to the forks as preventative maintenance? If it holds air, does anything have to be done? How do I check or replace the oil in the shock? How much and what type of oil do I use, so on and so forth.

Many Thanks,
Ian

Pretty much anything you need to do to the fork will involve taking it completely apart and rebuilding seals. That is when you will replace the oil. It shouldn't need all that. There are some forks that need a little oil on the dust seals occasionally, you'll have to check if that applies to yours. I don't know if any documentation is available on older Trek forks, you might check with a bike shop that is a Trek dealer, or maybe it can be found online. If it holds air, it's probably alright, though I've seen some bikes have an air spring in perfect condition but have problems with the damper. If you can get the parts and are willing to make a mess, rebuilding it would be a good learning experience.

They were made by Showa for Trek. Similar in design to the Rock Shox RS1, Mag 10 and Mag 30.

Does similar mean they use the same or similar parts?

Are you kidding? I live to make a mess and learn how to fix something. I wouldn't mind getting a rebuild kit (I doubt a kit is available if it's from 1995 or so). As for the quality, I know it's not as good as what is available today, but it is an air shock and like jediphobic said, is a good learning experience. I also think it will work well on my bike for me to piddle around on.

Thanks for the info.
Ian

The Showa forks didn't use the same parts, but they were assembled the same way. Does your fork have adjustable damping or just air preload?

I am new to suspension forks, so be gentle.

By air preload do you mean the air valve on the top of the forks? Yes, I have that. There aren't any other adjustments that I can see, top or bottom.

Boy is this bike dirty. Someone thought that taking a handful of grease and slathering the chain and chainwheels would make the bike run better. I don't know when the last time this thing was cleaned.

Ian

Wow. That thing looks a little corroded, but otherwise in decent shape.

You've only got air preload - that's the schrader valves on top of each fork leg.

It's constructed very much like the Rock Shox RS1. The Tech manual for the RS1 is here- https://mombat.org/Rock_Shox.htm -to give you an idea of what it's like to change the oil.

Since there are schrader valves on each fork cap, they should be easy to remove with a schrader valve tool.

Actually, there isn't any corrosion on the fork, dirt, yes, a lot of dirt and grease.

Thanks for the link, I'm going there now.

Ian