Cox burned engines - Help.....

Plastic bodies are just pressed on, albeit, some are very tight. You may have a little luck GENTLY wiggling it back and forth, but I hate doing that personally, but have done so in the past, and moreso if you want to reuse it. Just be careful of the opening for teh venturi as it is a weak spot. I am also currently having a problem removing one of mine currently that I would like to swap with an engine in better condition just to have a nicer looking engine. However, one must be careful as to not to break it when removing, if you plan on reusing it. May also want to soak in nitro fuel to soften the castor residue most likely holding it tight. And as for the NV assy, just grip the venturi by the hex under the flared end and twist it back and forth to remove if it is tight. They are just a slide on piece. However, with yours being in a fire, something may have warped slightly making it tighter than normal. Hope this helps.