Hi, well this is my first post here on gstwins, I've been lerking for a while tho.  I picked up my first street bike, a 2005 GS500F about a month and a half ago.  It had been dropped by the previous owner a few times, the rear faring was cracked and the rest of the plastic wasn't in the best shape, but the bike was mechanically sound, inspected, registered, and ready to ride. So far I've replaced the rear plastics, cut down the turn signal stalks and fenderectomized it as well as typical maintenance like oil, air filter, chain lube, ect. 

This is my first street bike and I've loving it.  I've been riding dirtbikes/quads/3 wheelers for years and transition from dirt to street was great.  Anyway today I had a weird fork issue while out riding. 

So I came to a stop sign fairly hard and heard a clunking sound in the front end.  About 5 mins later my forks felt very springy, like there was no dampening going on at all.  My bike was bouncing around from front to back, when I hit the brakes hard I could hear the same clunking sound.  It got so bad I pulled over and deemed it was too unstable to ride.  My dad came by and we trailed it home, good thing I was pretty close.  Nothing appeared to be leaking but the forks would compress completely with minimal force. 
I thought maybe a broken fork spring so when I got home I pulled the caps off and pulled the springs out, completely fine.  Oil was in good shape and there appeared to be enough of it and the same amount in both.  At this point I was frustrated so I decided to put the springs back in and do some research.  After I put the caps back on I noticed it seemed to sit a little higher then previously, I pushed down and the dampening seemed to return.  So I went for a ride around the corner, believe it or not but the front end felt better then when I got the bike!  Stiffer, less compression over hard braking and better turn-in.  And I tried some hard braking to see if it clunked and went out again but nope it was perfect.

Seems very strange to me.  But this is what I'm thinking: There was some sort of drit that could have gotten in the seal(s) and caused them to fail, and then when the springs were out and the fork compressed all the way down it dislodged whatever had caused the issue?  But idk.  Anyone know anything about this?

Sorry for being long winded on my first post!

Welcome Zach,

your fork thing could be as you described and just a one off... could happen again. I'm not expert on the forks yet so i'll leave that to the 'heads' .. good job on inspecting it right away and getting what seems to be a win on the issue already! . could be the previous owner had been messin with the forks and not done the job right? or wrong order of assembly? ..or just a glitch in it!

Do you know whether or not the PO had messed around with the forks at all? Maybe left something out of place?

Clunking is a bad sign, finger check all of the bolts on your bike to make sure everything that needs to be tight is tight.

If it keeps happening take a look at baltimoregs's fork seal replacement video here for disassembly and inspection:
http://gstwins.com/gsboard/index.php?topic=58403.0

From what the previous owner told me the forks were rebuilt by a local, reputable shop, but he did not have service receipts so what he says means squat to me. 
That is a great video about the fork seals.  I have some garage plans for the nepa winter including valves, cosmetics, and most likely better front springs, and I think since I'll have the time I'll rebuild the whole assembly with new fork seals, and do it right hahaha.