Check the easy stuff first, i.e. whether the gas tube is free of lead dust. The harder stuff is recalibrating the gas cylinder with a set screw. The hardest bit is to take the rifle apart for maintenance which is said to be tricky (but isn't, really)
I used to shoot my Revo down to about 110-100 bar. That takes about 5 magazines and the last magazine didn't always repeat well. I'd say 120 bar minimum for proper operation sounds about right.
Webley FX2000 .22 FX T400 .25 FX Monsoon .22 Walnut FX Cyclone .177 Regulated FX Biathlon .177 Regulated
Careful a lot of new owners shoot it down to low and may causes the breech seal to make a hard good bye down the barrel. Not knowing this they wonder why the gun stop cycling.