Powerhead 802

[Namscam]

just bought a powerhead 802 a week and a half ago and everything seems to work fine except for the fact that every 10-15 minutes or so it creates a burst of bubbles. I thought that it could have been the filter causing it or that it needed to be worked in, but after a week it s still doing that, so now i have taken out the filter and it is still doing that...I ve tried to play around with the flow valve and the reverse flow valve but its still doing it...Is it suppose to be doin that??