There is actually a function called BIS_fnc_setPitchBank, I've used it in the past to force an aircraft to dive or perform a roll, I've also used it to get the motorbike to do a wheelie.
// nul=[vehiclename] execvm "pitchup.sqf"
_obj = _this select 0;
for [{_p = 0},{_p < 30},{_p = _p + .1}] do
{
sleep 0.009;
[_obj, _p, 0] call BIS_fnc_setPitchBank;
};
To use it Place a function module on the map, and then in a trigger set to the radio and with this in on act nul=[vehiclename] execvm "pitchup.sqf"
The bike should pull a wheelie on command, to use it in your script though you will probably on need the function combined with the Key inputs, I have no idea how that would work.