Stihl 021 carburetor floods

hijust me again.all good in diaphram inlet valve spring assembly , but when in place and i blow through fuel inlet the valve shuts completely , however air still comes through a hole in lower department of carb body which corresponds to hole in crankcase, so fuel just oozes through inlet hose and into crankcase, Is there a valve between crankcase and fuel inlet pipe!

will answer this later for ya

You have a hole in the diaphram.

There should be pulsating crankcase pressure on one side of the diaphram and fuel on the other. The diaphram flexes with the pulses and pumps the fuel. From there it goes through the needle jet which acts like a float level needle jet in a normal carby, and into the second diaphrams chamber. Once the second chamber is full it closes off the needle jet so no more fuel gets through to the discharge ports/jets. As the fuel gets sucked past the high and low adjustable jets, and into the engine, the diaphram moves back and opens the needle jet again. The first diaphram acts as a fuel pump and the second one acts like a float in a normal carby.
Hope that makes sense.

If fuel is going from the inlet hose straight through to the sump, then there is a hole in the first diaphram.

at last a mechanic who knows what he is talikng about,right on the money

mechnificent
yes your assessment of how carb works is right , however situation is not as it appears.I purchased saw off TM and even though i did start it, i couldnt get any sense out of adjustmentsso i took tank filter out clean and tried again. still no, so i took carb out cleaned and the little filter too and needle valve , and put back, twice still no good , lots fuel around, so looking at 'exploded ' view noticed that the second diaphram, one with valves was actually missing.Got one from stihl and saw runs super sweet.
Thanks for yours and everone elses time