Carburettor Fuel Pump Spring?

[Vintage Engine Repairs]

First time coming across them on a 2 stroke (I see them on some 4t’s).

I have a Walbro WYL carb, there should be a spring under the fuel pump diaphragm, it’s missing. It has been working without, so I wonder - what’s the point in it?

Thanks.

 

[SteveSr]

First time coming across them on a 2 stroke (I see them on some 4t’s).

I have a Walbro WYL carb, there should be a spring under the fuel pump diaphragm, it’s missing. It has been working without, so I wonder - what’s the point in it?

Thanks.

You don't get as strong a pulse with a 4T so you need a bigger diaphragm and helper spring