Mk1 or Mk2.

I am only starting this procedure from the point when you have the valve assembly out of the buddy bottle (Stock). This is mainly because I am still having bad dreams about Thread Locker, Gas Torches and Melted Seals.

The procedure is much the same for the MK1 and the MK2 valves. The seal on the MK2 valve is a bit wider and it should have angled faces that match the valve seat. It looks like a fat version of the MK1 seal after lapping, seeDiagram 1. The MK2 seal should therefore require less work than the MK1 seal. Please be aware that I have not tested this procedure on a MK2 valve.

Discalamer.

If you wish to make any use what ever of this procedure you do so entirely at your own risk. You must take full and sole responsability for any loss, damage or injury that may arise for whatever reason from your use of any infromation you find here.

Equipment.

• A drill hand will do but slow power drill is better.
• A compress air source - pump or bottle.
• Brasso liquid metal polish - this polish is less abrasive than most chrome cleaners.
• Silicone spray - Obtainable from a car accessory shop.
• Silicone Grease - Obtainable from Gun Shops, Dive Centres or possibly car accessory shops.

Safety Note.

This procedure requires the use of a drill and Brasso. Safety glasses should be worn throughout and all power tools treated with respect.

Care should be taken at all times when handling compressed air or pressurised vessels. If there is and doubt about the fitness for use of a pressure vessel or its connections DO NOT use it. Have it tested and use it only if the test centre passes it as fit for use.

General Notes and Cautions.

• When working with PCP internal components or were high pressure air is present normal oils must not be used they may explode.
• Dust, grit and hairs must be scrupulously removed even a single hair can cause a valve to leak.
• If any grit or dirt is present during Lapping Step 7 the valve seat and the valve seal may be seriously damaged.
• "O" rings and seals should be assembled with just enough Silicone grease to make them shiny. The Silicone spray seems to work as an alternative.

Diagram 1.

Lapping.

1. Take the valve assembly to bits making careful note of the way it fits together so you can reassemble it later.
2. Slide the valve stem through the valve seat as shown in Diagram 1.
3. Squirt a little Silicone spray into the open end of the valve seal.
4. Push the valve seal onto the valve stem.
5. Mount the valve seat carefully in a soft jawed vice.
6. Shake the Brasso and pour a little of it into the valve seat. Carefully grasp the valve seal with the drill chuck and start the drill.
7. While the seal and valve stem are slowly rotating press the seal gently into the valve seat. Repeat as required until the seal matches the valve seat. The Brasso acts as a grinding agent and reshape the valve seal to exactly match the valve seat.
8. Pull the valve seal off the stem and remove the stem for the seat.

Notes.

At Lapping Step 7 take care to keep everything lined up, do not tilt the drill or valve stem.
You may have noticed that I have not said how long you need to work at Lapping Step 8.
That's because this stage is only finished when the assembled valve holds pressure.

Testing the Seal.

1. Clean all valve parts including the steel valve housing. It is imperative that all trace of dirt, grit, Brasso and grease be removed before assembling the valve.
2. Once all the parts are clean spray then with Silicone spay. Take care not to blow the seal and the "O" rings away.
3. Assemble the valve and try blowing through it with the "top hat" submerged in a little water. If it holds pressure, dry it and fit it to the buddy bottle. Remember the to fit the valve/bottle "O" ring first.
4. Test again, filling it from your air source to about 50 psi. If it still dose not leak you should be able to fit it to the gun and use it.
5. If it fails to hold pressure in Step 3 or Step 4 then you will have to go back to Lapping Step 1 above.

Gunpower recommend using a thread locker on the valve/bottle tread so the valve will not screw out of the bottle if the bottle were ever to be completely drained of air while it was on the gun. If you choose to use it do so only AFTER TESTING and ensure that the bottle is empty before any attempt is made to remove the valve.

Links.

Gunpower Stealth forum.

The Air Pit.

Gunpower.

Airforce.

Talon Airgun Hunting.

Tuning the Gunpower Stealth.

Special Mentions.

Thanks to Bob Craske for telling me how to do this in the first place and for good advice.
Thanks also to Hector Medina for keeping up the good work on the Stealth Forum