Syhpon unit

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Hi,
Fitted a new syphon unit and inlet pipe to my toilet cistern. (Close coupled toilet) New syphon unit because the toilet wouldnt flush properly and had to keep rapidly pumping the handle to get it to flush. New inlet pipe coz I broke the old one.
Anyway, the thing still doesnt flush on one push of the handle! What the heck is wrong with it?!
TIA

[chairobyx16]

Could be the water level too low? this prevents syphoning