Siphon toilet cannot have dual flush?

Thanks Jess.
Problem has been resolved.
Inserted an extra piece of rubber which is above the diaphragm. This piece of rubber ( i cut out the required piece from a tyre tube) firmly closes the air hole when flushing.

When the flush handle is released air immediately gets in via the air hole into the siphon and water stops to flow.

Essentially the diaphragm lift the water into the siphon. The other piece of rubber closes firmly the air hole which controls the half or full flush. If the air hole is not closed
properly there will be no flushing.

The strange thing with the problematic flush is that the required rubber piece to control the air hole was missing !

@ma
December 2008

Thank you for the input Jeff.

The half flush I realize is due to half flush control hole in the siphon. This hole should be properly closed when the diaphragm is up thus allowing a full flush.
If I plug this hole with a rubber stopper I get the full flush but now I dont get the half flush any more !!

I am not sure if the diaphragm is suppose to provide the perfect seal to the air pressure or an extra bit is required.

@ma
December 2008

You may have cut the new diaphram slightly too large.
When you operate the lever you lift the water above the diaphram into the pipe. The siphon effect then draws the water from the tank past the diaphram into the pipe. If the diaphram is too tight it may prevent the water from passing.

Jeff
December 2008