First off you are going to need some things.
3/8, 5/16, 3/16, 7/64, and 5/64
I recommend Dow33.
1) I find that if you remove your drop, it makes for easier disassembly and assembly.
2)Remove your HPR, by unscrewing it.
3)Unscrew the 4 tray screws located in each corner of the tray. Use a 7/64 allen wrench.
Tray Removal Tray Screw Removal
4)If you dont have PDS then skip step 4.
Remove the eye covers with a 5/64 allen wrench.
5)You need to get the ram out. In order to this you need to remove the bolt and bolt pin.
6)Unscrew the ram out the back of the marker. Make sure you unscrew all of the cap and not just the ram spring cap.
Ram Removal Ram taken out
7)Now, remove the LPR, Valve Spring, and Cupseal.
LPR Removal LPR, Valve Spring, and Cupseal
8)In order to push the valve out you will need to unscrew the valve screw and take off the ASA.
Unscrew the valve screw with a 3/16 allen wrench.
Valve Screw Removal Screw Out
9)Get a 5/16 allen wrench and find the allen screw up in the ASA.
Unscrew the ASA off.
10)Now, locate the valve from the back of the gun.
Valve Back View
11)Get something long and push the valve out the front of the gun. I find that a 3/8ths allen wrench is the perfect length for the valve removal.
Allen Wrench Pushing Valve Valve being pushed out front
12)Get your aftermarket valve and apply some lube to it.
13)Push the aftermarket valve from the front in, making sure the air outlet hole is facing up.
Push the valve in, until you cant go any further.
14)Put the valve spring back in, followed by screwing the LPR back in.
Valve Spring and LPR Reinstalled
15)Make sure the valve screw hole is lined up with the valve and reinstall the valve screw with a 3/16 allen wrench.
Make sure that the valve screw is not too loose, but not overly tight. It should be snug.
16)Screw the ram back in.
17)Reinstall your ASA, by lining up the ASA and screwing it in with a 5/16 allen wrench.
18)Once you get the ASA installed, get ready to screw the tray back on with a 7/64 allen wrench. Make sure all wires are tucked and wont get pinched.
No pinched wires/Tray Install Tray On
19)Reinstall bolt, making sure air inlet hole is down.
Air Inlet Down
20)[b]If you dont have PDS, skip this step[b]
Put the PDS covers and Oring detent back in. Make sure you dont pinch any wires. Use a 5/64 allen wrench.
21)Screw your HPR back on.
Screwing HPR Back On
23)Readjust the regs and go rip some paint!
Hope this helps some people out.