Theoben Rapid Forum

Here's a pic of a Joe Young Rocket valve setup for the mk1. It's the full kit including the mk1 fast flow . As you can see it uses a huge hammer spring that runs the full length of the hammer. There's no hammer pip as such - it's more of a tapered point to the hammer tip. The valve spring is over size too which sits inside the extended plenum that fits in place of the valve cap. The valve body is brass with large ports and the valve stem is a stainless rod with a delrin top hat.

Some people really do like the setup but it's massively over sprung and does produce quite a big power curve .....

Thought id put the pic on for information

i got the same setup in my bits box it was fitted to a mk1 that i got years ago

I've seen a few up for sale, a shop north of the border was asking £175 and a couple on the bay made silly money.

From what I gather the valve spring is a short hammer spring.