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1983lux 02-19-2014 11:05 PM

PMI Trracer powertube leak
Hey guys,

I've been trying to fix up my old PMI trracer, and have ordered some parts for it from Bacci paintball which I just got today. I put in a whole new brass nut into my valve assembly, complete with cupseal and powertube. Everything looks like its in great shape, and the valve nut assembly was advertised as 'tested, no leaks'. I can't see any marks at all on the cup seal, looks new.

However, when I screw the valve assembly onto my HPA tank, it leaks out of the powertube. If I cover the powertube with my thumb, it gets much quieter but I can still hear a very slight leaking noise. I've tried putting in a heavier valve spring I had lying around inside to 'push' the cup seal against the seat a bit tighter with no luck.

Is it possible that the low pressure in my tank (its only somewhere between 100-500psi according to the gauge) could cause the cup seal not to seal properly?

I'm thinking teflon tape on the valve nut threads might help the quiet leak I hear when I cover the powertube. I'll try re-filling the tank and putting teflon tape on the nut threads. Is there anything else I can try, or easy to obtain parts from other guns that might make a good cupseal?

bacci paintball 02-20-2014 12:54 AM

I messaged this as well but then thought it might end up helping someone else if I post it. Feedback is always appreciated if anyone noticed something I wrote that is incorrect or knows something I missed.

There are three points that may leak in your valve assembly.

1. The valve retaining screw oring. This oring goes around the brass piece that screws into the Trracers back bottle valve. Make sure it's slightly oversized and you feed a nice compression when you tighten down your valve retaining screw.

2. The hard plastic cup seal that is on the base of the powertube and the valve retaining screw seals against. If you checked this and the hard plastic seal is smooth then it probably isn't this. This would result in a leak down the barrel. (This is usually the first thing I replace if there is a leak).

3. The small tiny oring that is under the hard plastic seal and wedges between the seal and the brass cup. Might be this oring or it could be the powertube loosening. I would make sure this is tight. It would also result in a leak down the barrel.

And as you mention it could also be the lower pressure in the tank. Try the trracer with a high pressure tank (co2 or hpa) outputting between 650 and 800 psi and see if the leak still exists. Not enough pressure could cause the valve assembly to not seal properly.


1983lux 02-23-2014 03:24 PM


I've refilled the tank, but problem is still there. I've also replaced the large valve nut o-ring, and got another o-ring for the powertube nut. Leak is still there, which leaves only the cup seal as the main possibility. Its strange though, as the cup seal looks like a new one. Maybe I'll try lightly sanding and then using polishing compound where the cup seal seats, in case there is any tiny imperfections there I can't see.

I'm also curious about whether anyone has used one of these on a trracer with any success LAPCO Nelson/ Phantom CNC Machined Cup Seal | VIPs Save 10% & Free Shipping -

1983lux 03-04-2014 12:22 PM

UPDATE: Dan from Bacci Paintball sent me some free replacement cup seals and a new o-ring, which has resolved the issue! Very happy to have this gun working again, and I highly recommend Bacci Paintball to anyone searching for old gun parts. Ships quickly, great service, and very helpful.

sniperfan 04-11-2014 11:44 PM

Chuck up the cup seal with the seal facing out in your 1/4" or 1/2" drill. Spin the drill up to about 1/4 speed and hold a piece of 400 grit wet and dry sandpaper up to the seal for a few seconds. It will sand out the nick in the seal surface and you can reuse that cup seal right away.

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