Does anyone know where i can find instructions for how to put together a air retract system for a yellow f18 single. Also how stiff should to retract mechanisms be???? should i be able to check thier general motion prior to pressurising as mine are not budging one bit.

No, you will not be able to move them manually. You must pressurize them before they will function. That is unless you disconnect the air actuator from each retract assembly

What brand are they?