don't know what you're talking about, but my gixxer 600 easily pushed me forward in my seat when i blipped the throttle up and dropped gears in high rpms. all those rpms with the throttle plate closed really forces the rpms (and therefore speed) to drop rapidly
Same here, I have a brand new 2009 CRF honda enduro and it engine brakes super hard. I'm not revving it much either, enduro motors are all ohv single valve torque. At least this one is.
EDIT: Roommate has a Yammy 250 and it engine brakes just as forcefully.