Air shock problems, fork binding on return solution
I experienced the problem with fork stiction or binding on my Silvio (CBSV-054). Even @ 200 psi, the fork would collapse & not return until I got off the bike. Even then it would take 20 seconds or so to get to full extension.
So far, I've been able to get functionality back by a partial disassembly & limited pressurization. After stripping the fork from the bike, I pulled the rubber boot off the top to get access to the sliding shaft. I bled off all the pressure from the Schraeder valve. I left the star-fangled nut in place, but tried to remove the setscrews, on each side 3" below. The one on the left broke free after a bit of effort & I completely removed it. However, the right one wouldn't budge, no matter what I tried. I even tried to heat the area up a bit over the stove (mild heat, instead of a torch), thinking the aluminum tube would expand faster than the steel setscrew.
I also pulled the Schraeder valve off & was surprised to be able to exercise the fork thru its full range of motion. Looking back on this, I'm wondering if by removing the left setscrew, whatever stresses remained between the parts were shifted to the setscrew on the other side when the parts relaxed. I suspect the parts relaxation eliminated some of the binding in the fork motion, but also transfered more load to the remaining setscrew making it impossible to get out. [Note: Unfortunately, I stripped the hex socket after bending the hex wrench permanently.]
Regardless, the fork seemed to slide now with relative ease. After replacing the Schraeder valve, two strokes of the shock pump (an indicated 5 psi) caused full extension. At this point, I flipped the fork upside down & proceeded to inject lubricant at the shaft / collar interface. I then exercised the fork for about 50 or so strokes. I then bled off all the pressure & collapsed the fork. Again I attached the shock pump & again 2 strokes caused full extension. [EDIT: I don't think it is necessary to inject more lubricant unless you've got grit problems or intermittent smoothness. Then the lubricant would act as a cleansing agent.]
I wiped off all the excess lubricant from the shaft & collar, then exercised the fork (right side up) for 10 more strokes. It was at this point, I noticed an interesting artifact on the shaft. There was a thin, gray oil line on the shaft exactly midway in the travel. I wiped this off again, but it came back again after a few strokes. It seems to be the travel limit of the shaft wiper seal [Thanks, JT for pointing this out].
Finally, I bled off the pressure & reinstalled the setscrew & the boot, since things seemed to be working. Upon repressurization, 2 strokes again caused full extension, implying no more binding. Increasing the pressure to 100 psi, caused no real change, other than increasing the force required to move the fork. I left it overnight & 100 psi to see if it a) lost pressure & b) still functioned properly. No problems in the morning. [Note: rotate the boot so the 2 vent holes are perpendicular to the front of the bike. This will keep the vent holes from being directly in line with junk thrown up from the tire.]
Although some of the binding may be due to displaced lubricant or grit on the shaft, I think the main culprit is some sort of deflection or distortion between internal components. This may be residual stresses from initial assembly, but I suspect we may experience fork binding problems among heavier riders on rough roads & not among lighter riders on smooth roads as the aluminum components move relative to each other under load. Removing the setscrew seems to relax & eliminate the binding. Please note that this is not a factory suggested or condoned procedure; It is just one Silvio owner's experience & your mileage may vary.
I'll keep the forum appraised of the longevity of this success. For now, it's behaving very, very nicely.