The most important thing to do with this modification is to disable the blowback. There are a number of different ways to accomplish this, some that are very easy, and others that are more labor intensive.
First of all, blowback is caused when air is slipped by the valve pin and used to "blow back" the striker to lock in place for the next firing sequence. If this is still enabled, then the pump action is not work as the whole point of this mod is to "pump" the firing mechanism into ready position.
Obviously, to get rid of blowback, we need to correct the issue with the valve pin. If you look at the pin in a blowback gun, you'll notice that there is a flat area cut out of the end of the pin. Here is a picture of what I'm talking about.
You can see the flat part of this pin - it's the shiny part that allows air by to blow back the striker. The easiest way to solve this problem is to buy a valve that is designed for autocockers or for fasors. These bolts don't have a flattened area on them. The Trinity cocker valve pin or a valve pin for a T1 is perfect for this and only require finding and buying. No modifications would be needed with these pins. However, I searched for both these pins extensively on the internet and couldn't find a single one, so I was stuck until I decided to modify my stock valve pin. How to modify your stock valve pin
The easiest way to solve this problem is to buy a valve that is designed for autocockers or for fasors. These bolts don't have a flattened area on them. The Trinity cocker valve pin or a valve pin for a T1 is perfect for this and only require finding and buying. No modifications would be needed with these pins. However, I searched for both these pins extensively on the internet and couldn't find a single one, so I was stuck until I decided to modify my stock valve pin.
How to modify your stock valve pin
Here you can see that the flattened part has been filled with JB Weld and the pin itself is pretty round now.
Since I couldn't find those valve pins, I did the next best thing which is modify my stock valve. Fortunately, it's very easy to do and requires very little tooling. In fact, all you need for this modification are:
NOTE: When using tools and caustic agents such as JB Weld, be sure to follow ALL directions and safety procedures. If you are a minor, be sure to get parent permission first and have parental supervision. Never leave equipment on and unattended, and be aware that chemicals can harm you if used incorrectly. Be sure to wear proper safety goggles and go slowly.
The first thing you need to do is rough up the flattened area of the stock valve pin. Take the small flat file and run it across the entire area, including the raised area on the end of the flattened area. This is so the JB Weld has something to grab onto when you apply it. Otherwise, it's liable to break off the first time the striker hits it.
For this next part you need to have a good, open working area. You don't really want to do this where it may fall on your living room carpeting or get on your good clothes. JB Weld is a mess to clean up, especially after it dries!
You can get JB Weld at most automotive repair stores and retailers like Wal-Mart of K-Mart. It's relatively inexpensive - I think I paid 5.00 for mine. It'll last a long time also as you don't use very much of it for this kind of work. Follow the directions on the packaging for mixing up the JB Weld and like I said, mix it up away from good stuff you don't want to ruin!
Squeeze an equal amount of stuff from both tubes onto the flat surface you got to mix this on. Using the wooden stick, mix it up really well. You only have a certain amount of time to do this, so be quick about it, but be concious of what you're doing.
Once it's mixed, scoop a bit of it up and spread it on the flattened and recently roughed up part of the valve pin. Apply enough of it to completely fill in the missing area of the pin, but you don't have to be perfect yet. Just apply a little more than you actually need.
Allow that to sit for a few minutes - say about 5 - 10 minutes. It should be sticky, but still moldable. Mold it so that it rounds out the pin completely.
Don't worry about being perfect - that's what the sandpaper is for later. Once you're somewhat satisfied with the results, allow it to dry the recommended amount of time as found on the packaging. I actually let mine sit several days, I believe more than a week, since I got occupied with other things. It was good and hardened by the time I got to it!
To make this perfectly round, I used a trick I discovered several years ago when I was still polishing the internals to my Spyders. I took the cup seal off the valve pin, then clamped the valve pin in a cordless screwdriver. Take a strip of sandpaper and wrap it around the pin, and turn the screwdriver on. Apply a tiny bit of pressure against the paper as the pin turns, and this will sand the JB Weld down and smooth out the roughness - hopefully making the pin round in the process. Plus, it helps to polish the pin!
The top valve pin is unmodified and still has it's flattened part. The bottom striker has had the JB Weld mod done (it's the darker area.)
Check the pin by putting it in the valve and checking the tightness. You want it to move easily in and out, but not be able to see a lot of space between the valve hole and the pin. (Remember, the SMALL hole on the valve faces the striker.) This is why I used the higher grit sandpaper. I didn't want to remove much material at a time.
When it finally fits somewhat tightly but moves easily, you need to polish it. I used Mother's Mag polish from Wal-Mart. It's the same stuff that auto buffs use to polish up the rims and chrome on their cars and it's PERFECT for polishing parts in your markers. Rub it on with a small, clean cloth - in a circular motion which assures you get everything covered well. Then, I use the Dremel with a polishing wheel to buff it up. Be careful! This will also remove the JB Weld!
When this is completed, reinstall the valve and pin in your marker. But your marker's blow back isn't completely disabled yet. The final thing to do is to remove the oring from the striker. These two things should completely disable the blowback operating system.
You may wish to air up your gun and try this out now. Be careful to wait until the JB Weld is completely hardened, or you'll be doing this step all over again!