I get great service from ZDZ...and best you send Mike a email from their website..as it does seem they are visiting this forum area too frequently.
I rebuilt my carb (its too easy) and the rebuild kit includes a new diaphram.

Something to look at closely, is if the carb insulator block is cracked, you will not get the pulse needed to work the carb....I over torqued the mounting
carb screws and cracked it..not realizing how easy it cracks. Once I put a new one on...the engine worked.
Also if you had dirty fuel or a old tank that is deteriating inside..it can plug up the very small filter that is inside the carb..and you DO get a new
replacement screen with a rebuild kit.
Hope this helps....and hope you get some answers from RCShowcase rep here also.

Bobzilla