My XR400 runs 0 pressure. My XRl650 owners manual says not to run more than 6lbs. From what I remember, the XR600 is the same way. My brothers 95 XR 250 manual says to run 0 lbs pressure even though it has air fittings. From what I remember, my 86 XL250 was supposed to have 0 lbs pressure also but it has been 10 years since that one.
In all cases, the stock setup allowed the front end to dive much like you describe and that is why I say it is normal for stock XRs. They come from the factory with very soft springs with little preload and soft damping. The front end will easily sag 3-4 inches if you weigh much more than 150 lbs. Putting the correct rate springs in all of these XRs to match our weight eliminated the sinking front end. Even if his forks were "rebuilt" doesn't mean that they are sprung correctly
The air pressure is meant to be a supplement and I seriously doubt you could take the springs out of XR forks, pump em up, and go. I think you blow the seals and find yourself on the ground in short order. 12lbs may not be too much but I haven't seen a manual yet that recommends that much air. But I haven't read all of them yet so I could be wrong :confused:
Have your buddy take the springs out and measure them to see if they are sacked out or broken. You should obtain a manual that gives the service limit of the spring length. If possible, you should see if the springs are the original stock springs. If so, they are probably .38 kg springs with little preload. Your friend needs to find out what the proper spring rate is for his weight and make sure the preload is sufficient.
