My son has a Specialized Hot Rock and the front shock absorber is very stiff. I can barely get it to go down. It does have adjustment knobs on top of each shock, but seem to do any good. I noticed a allen head screw at the bottom of the shock, does it have to much fluid in them and can a drain some off by taken this screw off? Or is there another way to get these shocks to rebound.

Thanks for any help.