Ics mp5 sd
 

my mech box seems to be making a labouring weezing kinda sound making for a slow rof.

what does that mean ?

please advise

seems like the piston is stripped... you have to open the gearbox to find out.

It sound more like the motor height adjustment allen screw in the bottom of the grip in the center. If the piston is stripped you won't have any rate of fire. Have you by chance turned it in? if so, try backing it out 1/4 of a turn at a time, fire short burst and listen to the sound. Keep turning it out until it's quiet.