Had a leaking fork seal that I was able to clean out and stop leaking. How do I refill the fork with the correct amount of oil? Is it as simple as pulling the top cap, Dumping whats in there out, then refill with the correct amount?

 

Pretty much. While you have it apart that far, replacing the seal is not too much of a chore. Mainly under the top cap you will find a spring pushing the bottom have and top half of the forks apart, there's a nut under there and you push the spring down and slip a skinny open end wrench on the nut to hold it, then you can twist the top cap off, release the spring, and then remove the spring. The inner rod will slowly sink, don't worry about it just now, you can fish it out when it's time to reassemble. Pay attention to any spacers that might be under the fork cap between it and the spring, these will need to go back in the way they came out.

If all you are going to do is freshen up the oil, just dump it out into a bucket or something, and pump the lower half a few times to make sure you get it all out. Usually the correct amount of oil goes by "air chamber length". That is, when the top and bottom half of the forks are fully collapsed, you pour in the amount if oil that is necessary to achieve a specified air chamber length to the top of the outer tube. The normal way to do this is to over fill it by a slight amount, and then extract the excess oil with a fork oil level tool, like this one:

Motion Pro Fork Oil Level Tool | Dirt Bike | Rocky Mountain ATV/MC

This tool allows you to precisely extract the oil so that the air chamber length is just right. The shop manual or owner's manual should specify the air chamber length.

When filling oil, be sure and pump the lower and upper halves a few time to make sure oil is distributed throughout the system. Then fully collapse them and keep it vertical. Set the specified air chamber length on the gradations of the fork oil level tool, place the ring on top of the outer tube with the end of the syringe down into the tube, then use the syringe to suck out the excess oil until it sucks air, and at that point the oil level is set correctly.

To put it back together, you just need to fish the inner rod out, slide the spring over top of it, compress the spring while holding the rod up, get the skinny wrench on the bolt at which time that should hold the spring in place also, then put any spacers that were there originally back in place and thread the top cap back on the rod and tighten it up and remove the wrench to let the spring back in contact with the top cap. Lastly, slide the outer tube back up and thread the cap back on it and snug it up.

 

With the spring removed and the internals compressed all the way down, 101mm (4") from top of inner fork tube to oil level in fork. Then put springs back in and caps back on and re-install. You don't need any special tools, just find a precise way of measuring 101mm down from top of inner fork tube to the oil level.

 

. That makes it easy. I have done fox reservoir shocks for an offroad truck, some what the same on measureing the amount. Any specific oil I should use?

 

Stock is 5W fork oil. You "can" use ATF fluid if you're just topping up. A lot of guys use it. It's good to pick a brand and stick with it as some 5W are thicker than 10W. There's a good site with actual viscosities taken. Here's a read. Fork Oil Viscosity Chart, ignore the weight on the label. - Mountain Bike Review