How to change fork seals on usd forks on kwak meanstreak and how much oil to refill

The oil you want is SAE 10W-20. and 445ml if you are changing the oil. It can be more accurately checked with the fork removed and fully compressed and the spring removed, the oil will be 120mm from the top

You take the front wheel out then undo the top and bottom yoke pinch bolts,twist the forks downwards then undo the bolt in the centre at the bottom.then lift the dust seal out with a flat screwdriver and lift out the circuits you may need circling pliers.then pull the top and bottom of the fork apart quickly.it will separate.then change the seals and put it back together you need to install the new seal squarely and do not damage it.refill the oil by undoing the bolt at the top and pouring the fork oil in there.

If I have found the right vivavity model, then yes.
they regularly get rusy, need freeing, and refilling with oil.
See here.
http://www.scooternations.com/showthread.php?195-Freeing-USD-%28Up-Side-Down%29-forks

you need fork oil

To change the fork seals in a 2004 FXD you will need to remove the forks from the bike and then drain the oil and then remove the dust seal and the retaining ring and spacer from the top of the fork and then remove the Allen head screw from the bottom of the fork to release the fork tube and then using the fork tube like a slide hammer drive the upper bushing, seal and spacer out the top of the slider. While apart you should also inspect the rings and bushings etc. You will need a special seal driver to reinstall the upper bushing, seal and spacer and then you will need to accurately refill the fluid to the correct level/amount. FXD/FXDL uses 10.6 OZ or 0.31 cc of Harley-Davidson TYPE E FORK OIL (Part No. HD-99884-80) and the level measurement is 6.69 inches or 169.9 mm. Be very careful and accurate with the oil level as too much or too little will adversely affect the function, ride and steering of the bike. It is best to use a fork oil level gauge and set it so that the ring will sit 6.69 inches or 169.9 mm from the end of the tube and secure it at that position. If your gauge has a plunger cylinder on it push the plunger on the cylinder all the way in and then with the fork tube bottomed in the fork slider, insert the tube until the ring rests flat on top of the fork tube and pull the plunger out to suck up excess oil from the fork tube. If no oil is sucked up into the gauge cylinder you need to add more oil until there is enough excess oil in the fork tube to have an excess amount sucked out of the fork tube. In this manner the gauges and cylinder will accurately set the fork oil level. If you have a vacuum operated gauge such as with a tool that attaches to a vacuum brake bleeder you will set the tool at 6.69 inches or 169.9mm as with the other type of tool and operate it the same way to remove excess oil to a precise and accurate specified fork oil level which is very important as an incorrect oil level can adversely affect motorcycle handling.

make sure that there is no weight on front end carefully remove the big nuts on the top of forks they will have some tension on them because of the springs remove springs and pour fork oil in make sure u use the right grade of oil and do not over fill.as this will cause to much hydrulicing and blow ur new seals it is important that u get the oil level right good luck

Unless you've had your front fork assembly serviced recently, I'd guess you've got blown oil seals in the top of the sliders on your forks. If someone serviced your forks lately, they may have put in too much oil and blown the seals. You'll have to drain the forks, disassemble the fork tube from the lower slider and replace the seal in each leaking tube. Refill the fork tube with the designated about of oil for a "dry" refill. Use this figure because the fork tube was disassembled. When you simply drain the forks without a disassembly, you cannot get all the oil out and the refill quantity is less.

Good Luck
Steve

look at the fork legs at the bottom there is a bolt on both legs its only a small bolt,,, undo this bolt and the fork oil will drain out,, to refill the forks take the top nut off the fork leg near the handel bars,,,,,,dont over fill with oil,,,and only use the proper oil,,or the seals will blow out and the forks will be very stiff

hi non usd forks are ok thers a allen key bolt at the bottom of the fork leg would be wish to change the fork guilds too thr fork seals can be prized out with a screwdirver carfully

What weight oil? 10w or 15w is good for fork oil. Also check that your valve that controls the oil passing back and forth is not obstructed inside the fork tube.