HOW TO: Robtown Air asst valve install - PbNation
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Old 03-12-2007, 12:36 PM #1
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Join Date: May 2004
Location: Lone Star State
 has been a member for 10 years
HOW TO: Robtown Air asst valve install

Ok, just to give credit where credit is due, some of these pics are Nitros, and I just used them as a matter of convenience instead of retaking and uploading pictures that show the same thing. He did a nice job, so I use his. Now, most of the pics are my own and I took them myself. I'm sure it’s obvious which ones are mine.

Anyhow, I recently acquired my Robtown air assist valve and hammer kit. I must say, this kit is awesome. Keep in mind I just installed it though, and I have encountered zero issues so far. So lets get started.

Good luck on your install, and if you don’t feel comfortable doing this….STOP….send it to Jared at DC. I'm not responsible for your gun if you mess it up.

You need:

3 prong tool
AKA lube
Paper towel or rag, and q tip
Spanner wrench (crescent wrench for 04s)
Robtown valve kit
Blue removable loctite

First the money shots…..weight difference between stock hammer kit and the robtown hamer kit.

Stock = 39.7 grams (included a bumper, probably negligible on my scale)
Robtown = 12.6 grams

That’s 31.7% of the weight of the stock, or a 68.3% reduction in reciprocating mass…..AMAZING. The hammer itself is insanely lightweight. As others have said, it feels like plastic. Its unreal.

Stock Hammer

Robtown Hammer
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Old 03-12-2007, 12:36 PM #2
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Location: Lone Star State
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Ok, now how to install.

Step 1:

Pull your bolt pin up. Remove your hammer cartridge using the 3 prong tool. When you get your hammer unscrewed as far as it will go, put your bolt pin in front of the hammer and push it down, then use the boltpin to push the hammer cartridge out of the gun. Kinda like Nitro did in this pic.

Step 2:

Now remove the front cap on the valve side of the gun (or Mitey Max if you have a MM).

Step 3:

Remove the valve setscrew that is holding your tornado valve. Like this. Then push the valve out the back of the gun using a chopstick or something that won't damage your valve.

Step 4:

Clean the entire right tube extremely well. I used a paper towel and a chopstick. Whatever you use, just be sure that you don’t get any sand/debris/or paper towel chunks stuck in the holes that feed the hammer or the ASA area. Should look like this now.

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Old 03-12-2007, 12:38 PM #3
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Join Date: May 2004
Location: Lone Star State
 has been a member for 10 years
Step 5:

Disassemble your hammer catridge. On 03s you need a spanner wrench, 04s have a hex cap on the hammer cartridge, which is much easier and requires one less tool.

Step 6:

Remove the hammer internals carefully. I did mine over carpet or a towel or something. If the hammer is stuck in there, you can tap it out into your palm. It will look like this when you get it out. Then clean the inside of your cartridge w/ qtips.

Step 7:

Now for the hard part, remove the hammer weight from the hammer shaft. From my understanding, they are red loctited from the factory. Whatever you do, don’t score up the shaft or brass fitting on the tail in of the shaft. You will want to store away your stock hammer incase it is ever needed in the future, or if you sell your gun, and the new owner wants it. Then remove all the orings/bumpers/stops from the stock hammer. It will look like this. Robtown hammer is above the internals, stock is on bottom. Parts are in order from left to right on how they should be put on your hammer.

Step 8:

You will now need to put the internals on in reverse order on the new hammer. I put the small bumper on the shaft first. Then put the tophat stop on (this stops the forward stroke of the hammer w/in the cartridge). Put the tophat stop on concave side down so that the bumper seats inside of it. Now put the UR70 010 oring on the tail of the hammer. Apply a bit of AKA lube to the tail oring. Then put the other UR70 010 oring in the countersunk side of the cartridge cap and put a bit of AKA lube on it as well. Then slide it over the hammer shaft. Apply a small drop of blue / removable loctite to the threads on the cap threads. Then tighten the cap onto the cartridge, but don’t overtighten. Then slide the large bumper onto the hammer shaft (in between the hammer weight and the cartridge cap, this stops the backward stroke of the hammer). Then put a drop of blue loctite on the threads where the hammer weight threads onto the hammer shaft. I didn’t take a picture of the robtown one after I finished, but here is the stock one. This cap should be screwed into place though.

Step 9:

Install the robtown valve using a drop of AKA lube on the outer orings of the valve body. Make sure when you put the valve in that you line the hole on the valve body up w/ the hole in your gun where the valve setscrew goes. Notice the valve hole is facing same direction as the setscrew hole.

Step 10:

Put a drop of blue loctite on the valve setscrew and secure the valve in place with it. Then replace your valve spring and front cap. Then replace the hammer cartridge and bolt, and then air it up……..NO LEAKS right. Well, I didn’t have any. If you do it right, you won't have any either.

Now all you have to do is fine tune your LPR, dwell, and HPR to get a consistent, safe velocity.

My settings are:

03 viking
Humphrey solenoid
Dwell = 9ms
HPR = ?
LPR = 69-70 psi
Chronograph = 275-280 fps

Every gun is different, but these settings work well for me. BE SAFE AND HAVE FUN....Thats what its all about!

Last edited by yakitori : 03-12-2007 at 12:44 PM.
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