Airmaks Caiman - a definitive regulator fix!

[JimD]

My Caiman X is more recent and looks like your pictures. The "secret" to the modification is to create a path for air to vent from the washer area of the regulator. The first possible blockage point is the bottom of the regulator piece. It seems to be so well machined that it seals on the block it screws into. I filed V grooves like I think was pictured but a small hole like the vent hole on the airtube should work. That did not fix things for me but helped. I also needed to create a little path in the threads to the vent hole. I screwed the air tube together and used a small drill bit in the vent hole to mark the nut. Then I made a very small path through the last couple threads to the point of the hole in the airtube. That plus the V grooves I filed first gave me a nice flat shot curve. ES typically under 20 now for several magazines of shots.

 

[Lbnazty]

JimD , Thank you for the info. I modified my Plenum as shown Below, At 1 spot I drilled through air tube vent hole to mark the spot. I took a dremel with a carbide bit to to remove a small area and part of thread. The black you see is a sharpie I used to mark the spot so when I screwed the Plenum in I would know the relief would line up with the vent hole. I took a file and filed a very shallow groove as shown in arrow 2.
This had a very small different s in Shot string velocity , within a 20-30 shot spread it is within reason . Over a 120 shot spread it goes from 915 to down to 815. This seems ridiculous for a so called regulated gun.
I am not sure what my next steps are, Should I pull the regulator & check that?. I am new to all this , but , mechanically inclined.
I am not sure I understand where you put you're grooves., do you have a picture?. For my use, the gun is plenty accurate enough, I am just frustrated cause I know it is not right & could be better.
Thanks for Any help.

 

[JimD]

Lbnazty,

I looked and I don't think I have any pictures from my modified parts. I think that is because the pictures already in the thread are so good. Post 20 shows a groove you are apparently reluctant to make. I think it is your missing link. There has to be a path from air around the washer stack to vent to atmosphere. The end of that plenum piece is so flat and the mating surface so well machined that it can seal and the washer area does not vent. You could also try a small hole about the size of the vent hole in the pressure tube in the end of the plenum piece but it seems easier to just file a groove. I believe I filed more than one. There seems to be no drawback to filing a fairly shallow groove.

 

[Lbnazty]

JimD,
When I looked at the regulator I thought the tiny hole on the side of the regulator right after the o ring on the end was the vent for it . This is why I filed the groove along the outside of the Plenum. I Simply did not understand how the regulator works and vents. I tried looking for a good explanation, but , so far haven't found one yet,
I don't understand how the regulator vents on the inside of the Plenum.
So what you are telling me is you filed a slot on the end of the plenum as shown in the original Weevil Post.
I will Try that next as you have verified there are no drawbacks.
I have sorted the trigger out & also adjusted the hammer spring. When I get the regulator problem solved I will be happy with this Gun.
I will modify this tonight & test probably tomorrow.
Thank you for your Help

 

[Lbnazty]

Added the groove, Shot string pretty much the same. starts out at 944 FPS after 10 - 20 or so shots drops to 922. I dry fired to get tank pressure to about 160 bar. Shots are in the 860 Range. At the 130 bar mark the shots are in the 845 or so range.
So, Modification have had little to no effect, Still the declining Shot string FPS from 300 bar down to 120bar approx 120 shots.
I am waiting on more pellets, I am out of the 18 grain.
My thoughts so far Is that The regulator is not operating properly, I need to find some info on how they should be.
Is the regulator bad? In my limited experience, this does not seem right to me.

JimD, My gun in missing the grub screw as shown in picture, do you have one there?