If it's the old style valve , I always had trouble with them , usually caused by sand or salt under the rubber diaphram. I sometimed got results by placing them in very hot water then removing and rubbing fairy liquid roung the edge of the diaphram. Have you talked to Henshaw about the problem ?
Took your advice and rang Henshaws who have sold me for 5 sterling a special spanner. This is like if all else fails read the instructions. Thanks for lateral thinking
My lateral thinking only goes so far upwards. What does the special spanner do?
I have a Tinker Traveller with a leaking valve-does it need a different special spanner?
Some Tinker models have a valve that screws out and you need a special shaped spanner . I believe my model to be apprx 1990. Thay are also sending me a new valve kit.