About 5years ago the fuel cap on my McCulloch Trim mac 250 started leaking fuel through the vent hole in the cap for no apparent reason. I bought a new cap and all was fine until today when I realised that fuel was dripping out of the vent again.
There are no apparent cracks in the cap. The central vent ?plug? looks to be composed of partially fused metal beads. Any ideas why the vent is failing like this? It just seems to ?happen? for no apparent reason.
Is there any way of restoring its fuel retaining properties whilst retaining its air admittance properties? It?s no big deal as replacement caps are available on eBay but I?m just curious as to how it works and why it fails.
Tim