I think I’ve found out why my fwb was only making low (and variable) 500s : https://i.imgur.com/56Q3pev.jpg



(Actually that was only half the reason. This was the other half: https://i.imgur.com/LgoLf6Y.jpg. But I’ve sorted that out)

Does anyone have experience of the replacement springs sold by John knibbs please, or any other suggestions for replacement 300s springs? Many thanks.