Introduction: Replace the Valve Seat O-Ring in a Paintball Marker

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For those of you that do not know, paintball is a sport developed in the late 1980's where players try and shoot each other with paintballs. Paintballs are gelatin capsules filled with a non toxic dye, usually .68 caliber. The players use paintball markers, which use compressed air or CO2 to propel the paintballs.

Old paintball markers were like a lot of old things, built to last. Yes some were cheap and plastic, but there were some quality all metal markers made in the late eighties and nineties.

My paintball marker is a Tippmann 68 made between 1988 and 1991. Tippmann has been making paintball markers since 1986.

Step 1: O-Rings Get Old and Crack

After time, the O-rings in paintball markers get brittle and crack, causing leaks that make the marker unusable. In this Instructable, I will show you how to replace the valve seat O-ring in a Tippmann SL-68. There were many different paintball guns made over the years, but they all use some type of O-rings and/or cup seals that you can still get replacements for. Your old paintball marker may be different from mine, but you can still fix it and keep it running.

Step 2: Tools and Supplies

I only needed two allen wrenches, 1/8" and 3/16".

I had some paintball marker lubricant "K C Troublefree". There are many different brands but make sure you use paintball marker lubricant. It is formulated for paintball marker O-rings and copes with CO2 better than other lubricants.

I also used one O-ring from a kit that came with all the O-rings to replace every O-ring in the marker. They are available inexpensively online. I got mine from

Step 3: Loosen the Barrel Retention Screw

Make sure there is no air or CO2 in the gun before doing any maintenance.

Loosen the barrel retention screw.

Step 4: Remove the Barrel and Bolt

Slide out the pump, barrel, and bolt. They will all slide out together.

Step 5: Remove the Bolt/Hammer Spring

Tilt the marker forward, and the Bolt/Hammer Spring should fall out.

Step 6: Remove the Hammer

Removing the hammer requires that you depress the sear while also pulling the trigger.

Step 7: Remove the Valve Assembly Retention Screws

There are two Valve Assembly Retention Screws, one on each side of the marker.

Step 8: Remove the Valve Assembly

Tilt the marker forward and remove the valve assembly.

Step 9: Inspect the Valve Assembly

Now that you have the valve assembly out, you can inspect it. My marker's valve assembly has a cup seal and a valve seat O-ring. My valve seat O-ring was cracked.

Step 10: Find the Right Size O-ring.

You could possible find the right size O-ring at a hardware store or auto parts store, but I got mine in a kit found online. I found the right size O-ring from the kit.

Step 11: Install the New O-ring

Put some lube on the valve assembly and slide the new O-ring into the grove on the valve assembly.

Step 12: Reinstall the Valve Assembly

Reassembling the marker is the opposite of disassembling it starting with installing the valve assembly.

Step 13: Snug the Valve Assembly Retaining Screws

Use your finger to hold the valve assembly in while snugging up on the valve assembly retaining screws. Do not tighten the screws yet, we will do that at a later step.

Step 14: Install the Hammer

You will have to depress the sear and pull the trigger to install the hammer.

Step 15: Install the Bolt/Hammer Spring

Install the bolt/hammer spring.

Step 16: Install the Barrel, Pump Handle, and Bolt

With the pump handle on the barrel, hook the pump rod into bolt and install them.

Step 17: Tighten the Barrel Retaining Screw.

Make sure the barrel is fully seated into the frame and tighten the barrel retaining screw.

Step 18: Tighten the Valve Assembly Retaining Screws

Depress the pump all the way in, to hold the valve assembly in place, while you tighten the valve assembly retaining screws.

Step 19: Enjoy Your Repaired Marker

Get out and enjoy your marker. Be prepared for questions like, "What is that?, How old is that? "Where did you get that?" And have fun playing with a paintball marker that is almost as old as the sport of paintball itself.

Step 20: Video

As usual, I made a video.

Thank you for watching and enjoy.

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