When I put my motor back together mine did the same thing when I released the tensioner. It would rotate the cam just slightly. I played with adjusting over a tooth, and no matter what I did I could not get it perfectly parallel when the tensioner was engaged. It would be ever so slightly angled in one direction, move it over a tooth, then it was ever so slightly angled the other direction. I think that is just the way they are. I haven't had any problems with my motor like this.
Name: Shane
-2011 Polaris RZR-4 800 (SOLD)
-1999 Polaris Sportsman 500 ATV
-2006 AC Prowler 650XT (SOLD)-- updated bevel gears, updated oil pump driven gear, 4 wheel disc brakes, line lock E-brake, Papa Slap clutch, Xentec HID's, Dynatek CDI, Warn skid plates, Intellitronix gauges, 2010 intake/cvt duct work and dust shield, RZR seats, Bestop folding windshield, full cab kit, rear cage and rear seats (4 seater)