Canadian Airgun Forum

My cousin found a beaten Crosman Mark I at a flea market. He tried to re-seal it and was not successful. He told me that the CO2 escaped through the valve and that if I wanted it he would give it to me.

I completely dismantle it except for the piercing assembly. As the paint was badly flaking I decided to glass bead it. This produces a matte gray finish. It is not as exciting as a polished mirror finish but it is good enough for me.

After reassembling it, I installed a CO2 cartridge and discovered that once pressurized, since I fixed the leaking valve, that there was another problem (which is a leaking push button piercing assembly).

I was expecting that after piercing the cartridge the pressure would make the button pop up and seal but it didn’t happened.

Since I own another Mark I, I swapped the piercing assembly. This one has a small lever which can be moved back after piercing and I obtained a seal. This allowed me to shoot and start readjusting the sights.



I would prefer to use the piercing assembly that came with the pistol. The diagram is not really clear, I know that there is one O-ring outside as I could see it and it is identified in the list. It seems that there might be another seal that goes around the piercing pin but to access it a retainer pin must be removed first.

It is a really small, but fairly long, pin and my 1/16 brass punch is not strong enough to push it out (I just bent up my punch).

Any suggestion to drive this pin out?

Thanks.

R-Gun Pete

Try removing the star lock-washer that you will see around the piercing pin. This is part #10-090 in diagram. Then slide out part #10-082. Then you can carefully pick out the small urethane o-ring (#125-047). The o-ring should be size 005. Urethane is best but even nitrile will work for a while in this application.

Parts diagram http://my.tbaytel.net/coopers/CrosMkI/FSB-1982.jpg

My complete review http://my.tbaytel.net/coopers/CrosMkI/review.html

Hi TCooper!

Thanks for the reply.

I had already discovered your site and used some of the info I found there for my repair. It is very well done and a good source of information.

Another source that can be useful would be the Service manuals.

I was not sure if was necessary to remove the locking pin and the piercing needle but as you mentioned the o-ring can be changed without having to. It is a good thing because this morning I also tried with a steel punch to no avail. This one too got bent.

Anyway thank you again. I removed both parts that you mentioned and discovered the disintegrated old o-ring. I will install a fresh one later tonight when I am back home.

If you are interested in the Service manual for 2 different versions of the Mark I, those are the links:

http://s39.photobucket.com/user/airgunf ... t=3&page=1

http://s39.photobucket.com/user/airgunf ... t=3&page=1

Have a nice day.

R-Gun Pete

As explained in my other question, I encountered another problem. I am posting the solution in this thread too.

So, after releasing the CO2 through the piercing cap (because the pistol didn’t want to shoot at all) and spending one hour trying to get out the retaining star that hold the fine screen, I discovered that the cause of the non-firing was not a plugged screen as I first assumed.

It was evident because there was a big hole in it. I also checked my other Mark I and effectively it has a hole too. I then decided that I would not re-install it.

Since this potential cause was out of the way, I recapitulated what I did.

I resealed the pistol using the black o-rings from my Princess Auto kit as I did for a couple of Crosman T-38.

I know that some o-rings will swell in presence of CO2. When they are captive in a groove it means that they even seal better. In the case of the Mark I, I used one for face sealing with the face of the valve.

This was the culprit. I came across some pictures of repairs on the web and it seems that it is a flat seal that is a harder plastic (and not an o-ring) that should be used.

When I started, the o-ring was not swollen so the end of the shaft that is hit by the hammer was sticking out enough. After being exposed to the action of the gas (toward the end my shooting session), it started to shoot weaker and finally stopped. Now, I know that the end of the shaft was not sticking out anymore.

A solution, to make a homemade seal that works better and is not subject to swelling, is to use a plastic cover from a coffee can or a Nestle Quick Can. It is smooth, slightly flexible and also the thickness is not too bad).

The trick is to have cutting punches of the right sizes (Princess Auto again) and to center the small hole for the pin so it is concentric with the outside.

After applying a thin coat of silicone grease to the shaft and the plastic seal, it worked perfectly.

I was able to finish setting the sight and had an enjoyable shooting session with my new (old) toy.

R-Gun Pete