I had sent a pm to mmracing about putting new oil in my forks and the steps to do it. He replied with a great deal of info like always and suggested I start a thread.
Here is the info he sent me. Thanks again for all your help mmracing. Remove the front wheel. Loosen but do not remove the fork cap on top. Remove one fork. Remove fork cap. Pull fork spring out. Dump oil out in a measuring cup. Pump fork to get all the old oil out. Use 30W fork oil. Clean measuring cup out. Increase volume of fork oil going in by around 20cc. This keeps the fork from compressing as much. Pump fork to get all the oil back in. Put fork spring back in. Put fork cap back on. Put fork back in triple clamp. Tighten fork cap and repeat the process on the other side.
One thing I did on a copy of an xr fork (Chinese knockoff) to slow the fork down was pulled the damping rod and epoxied one of the holes in it. Closed it off. It slowed the fork down and stopped the bike wallowing around. I have heard of people blocking off the holes and re-drilling holes to tune how fast the fork reacts.
I knew guys that just went to 90w gear oil... I was waiting to hear one of them took it one step further and just loaded their forks with lithium grease.
Actually, 90W gear oil is not that far from 30W suspension fluid, depending on the brand. Gear oils and hydraulic oils (as suspension fluids are classified) are rated on different scales. Check here for a nice visual graph. The various manufacturers of suspension fluids seem to each have their own viscosity index. A 10W fork oil from one manufacturer might be WAY different in viscosity than a 10W (labeled) from another company. There's a lot of information here: http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid#Viscosity_Index but the really useful part is the ASTM viscosity chart on that Wikipedia page.
