front forks

I recently bought an 81 xj750 seca, got it running for the first time since 90'. I started tearing it down to bob it out, Question, what is that unit at the bottom of the front forks? I took it off and fluid ran out. Im assuming its fork fluid? how do I fill them back up? first bike im a newbie

 

That's the front fork anti-dive device, and that was brake fluid that dribbled out.

When you use the front brakes, brake fluid goes to the calipers and to a plunger valve assembly in those ant-dive units, which, due to the brake fluid pressure, "stiffen" the front fork and keep it from compressing as much as it would otherwise........the brake fluid pressure helps to "stiffen" the front forks at that time.


So it's time to flush and re-bleed your brake system, which it probably needed doing, anyway.


Might be a good time to rebuild the calipers, etc. while you're at it......

 

There's also an adjustment on the bottom of the anti-dive assy. You can adjust the amount of pressure to the forks when the brakes are applied.
You should get a shop manual of some kind if you plan to restore the bike. It will make things go a whole lot easier. Haynes or Clymer make good manuals for these bikes.