What oil to run in a rear shock??

[PowerJoe]

I have been using 5wt. Torco Fork Fluid in my forks and in snowmobile shocks in the past. What oil type or weight is reccomend for the rear motorcyle shock? I have a 2002 CR250 and I am also rebuilding a 2001 YZ250 shock.
In general I have been told to run heavier weight oil for longer rides or races, is this true? I run about 15 minute motos and I am an average rider.
Also what should the nitrogen pressure be? The Yamaha rep told the local dealer that it should be 225 psi, but I have heard people say as low as 155 psi.
Can anyone help me out or tell me where this info is available?

Thanks,
Joe

 

[marcusgunby]

You can use 5 or 2.5wt , it doesnt make a big difference(for a stiffer setup you can even use 7.5wt) as for the N2 pressure most use between 145-175psi.I use 160psi as a rule, as it falls in the middle of those settings.225psi is for something like a XR600.