Quote Originally Posted by T 20 View Post
There's either a vent hole at the end of the pump stroke or the piston head moves forward far enough so that it breaks cover in the cocking lever slot to take in air.

The vent hole in the cylinder is small enough and finished well enough that it causes no wear on the seal.

I've never seen a multi pump with a one way valve in the piston head to allow air in, it would just be an over complication that's not needed.



All the best Mick
yup. The only times I have seen valves in piston heads is to dump air when over pressurised, to prevent them going OTT... nothing to do with air intake... quite the opposite in fact !