STOP shooting light pellets you will overheat and ruin the seal
unless you lower the power via lower ram pressures the HW90 is too much power and will break scopes, melt piston seals and generally eat it self shooting light pellets at full power and pressure on ram
you need a shock pump and a fill fitting to refill the ram if you lower it too much
http://www.bestfittings.co.uk/shopexd.asp?id=638
http://www.bestfittings.co.uk/shopexd.asp?id=634
example but its entire ram fill kit
if ya can find a fill probe a shock pump can be set up to fill HW90
http://www.bestfittings.co.uk/images...01_ALT1LRG.jpg
US source for fill fitting
https://www.rapidairweapons.com/xcar...cat=255&page=1
https://www.rapidairweapons.com/xcar...ype=P&id=17629