Thanks for your quick reply guys.... Flypaper (Sorry i dont know ur name!!) one question though,
Will the side plate be open or closed for priming? What about after priming? How do i use the side plate? The fuel tank is right behind the engine but its a GP tank with the position of the fuel pipe somewhat lower than that fuel inlet on the needle valve assembly.
Also the nozzle to attach the pressure pipe has screw threads on them.

Sorry for asking so many ques guys but no one out here has seen such a muffler and hence cant help me!!

(P.S: How does the back pressure develop when running the engine if the muff is open throughout?)