kwik

For me it has allways been the pump-membrane, not the diagraphm operating the valve to the chamber.

The small lips tends to curl up a bit. So they dont close completely, and the pump action is lost.

This engine has been in storage for a year, and the tank was empty while in storage.

It is rather funny;
For years I have been told by the zenoah veterans to leave some gasoline in the tank, so that the membranes dont dry out. So I have done that.

But now, this time, I stored it dry,because what is said in the Saito manual;

Quote from the Saito manual;
"But in such way of storing, gasoline accelerate degradation of rubber parts such as diagraphm".

And still this happens.
The same happened to a brand new Valach 120cc inline twin, fourstroke; It had been testrun at the factory.
Then I have had it for some months, and when I tried to start; No luck. Only run the fuel I injected directly.

So replaced the membrane with a K-22 kit, where the membrane is white=> probably mylar. All ok.

So one wonders why they still push out HDA 48D carbs in 2015 with the rubber stuff.....

Maybe a tactic from Walbro to keep all the chain-saw repair shops in business?