What’s this and how’s it work
 

Can someone tell me what this does and is it needed
Sounds like something is loose internally in the black cylinder
Thanks

Fuel vapour trap I believe.
Don't know how it actually works and when ....?

I assume they are a carbon filter and if so they would be service replacement. It goes on one of the breathers from the tank.

I think the filter must be in the black cylinder
Not sure what the white valve is for

If there is something loose it will be a ball valve (or a loose filter!)

So it probably collects vapour, when enough vapour turns to liquid and fills the black cylinder the ball valve will lift and return fuel to the tank.

👍🏻👍🏻👍🏻👍🏻👍🏻

its a roll over valve, the loose thing is the ball so that when you roll it blocks the pipe to stop fuel coming out

Steve