When I check the compression I get 150 psi in both cylinders when I have the throttle wide open, yet very different readings (120 left and 80 right cylinder) when the throttle is left closed. Is 150 psi normal for an R90/6? And, why the difference with the throttle open and closed? My Clymer manual does not say to open the throttle, neither does the BMW manual that came with the bike. However, the Chilton manual does say to twist the throttle to wide open when testing. I am using a new screw on compression tester and testing after the bike has been warmed up. Also, I pull both sparkplugs. Any thoughts?