Posted by Mark Rogers on October 01, 2001 at 00:51:37:
I just purchased a
Tau-200. It will not hold gas. When I put in a 12g bulb, it leaks through the
valve into the barrel. I also tried a bulk fill with the same results. Does
anyone have any idea as to what might be the cause? Yes, I am filling it with
the bolt cocked, as per the manual. It has filled a couple of times and shot
very well, however, after about 40 or so shots, it started to leak through the
barrel and then refused to fill, leaking the entire Co2 bulb through the valve.
Any help would be appreciated.
Mark
Posted by Warren on October 01, 2001 at 11:46:59: I hope this will be of use;
I have heaps of experience with the TAU 7 but none with the 200.
I'm not
sure with the 200 how to get the guts out of the receiver. If it is like the
pistol, there will be a screw directly behind the line of the hammer spring/gas
valve, probably with a rubber o ring (when you remove this it will probably need
replacing, but there should be a new one in the spares that came with the
rifle).
If the gas valve does not fall out when you point the barrel to the
sky, you might have to cock the action and fire it out using hammer spring power
- just make sure you don't lose it when you do.
Typically the gas valve has
a bearing surface that is supposed to seal against a white neoprene ring. As
they exit the factory these are normally quite rough on the bearing surface (the
angled bit). It will have chatter marks, and quite frankly it makes me wonder
how they seal for as long as they do...I polish this surface YERY CAREFULLY
by putting it in the chuck of a lathe, bench drill, hand drill, whatever (try to
have it held fast so you have both hands free to do the polishing). Then spin it
as fast as you can, 1500rpm is good. Using a straight edge as a backer, (like a
small steel ruler), polish the angled surface slowly with worn 1200 grit paper.
It's VERY important that you keep the angle of the ruler/paper exactly the same
as the angle of the bearing surface. You should be able to get rid of all of the
chatter marks, and have a surface as smooth as glass.
Now, hopefully you can
reach far enough inside the action to clean out any oil, dirt, whatever, from
the neoprene white seal. Do this very carefully with a cotton bud or the like.
Next, you must seat the new surface of the valve with the white seal. Do
this by dropping it into place, cock the action so the hammer spring doesn't get
in the way, then take a drift, punch, or something that will fit down inside the
chamber on top of the valve, and tap gently a few times with a light hammer.
Now, reassemble, follow the usual instructions, hold your breath and hope
that it works.
Whatever happens DO NOT try to remove the white seal? It
takes a special tool from the factory, and really once removed should have the
face cut with another factory tool. I don't have these tools here in the US, but
will probably be investing in them sometime in the future.
And if all else
fails, email me and I'll help if I can.
Warren
Posted by Chuck Marsh on October 01, 2001 at 13:13:45:
Mark,
It sounds
like the Co2 poppet valve is stuck open. I would spray some WD-40 into the
reservoir and dry fire the rifle about a dozen times.
This will probably free
up the poppet valve.
This will only take about 3 or 4 minutes.
The only
other thing I can thin of is that the rifle has been taken apart and the hammer
linkage inside is not installed properly.
Regards
Chuck Marsh
Posted by Warren on October 01, 2001 at 15:19:37:
Sorry Chuck, but 90% of
the leakage problems we ever had with TAUs it was BECAUSE some form of lube had
found its way into the reservoir. The valve will not seal against the seat if it
has an oily residue.
As I said before, all my experience is with the
pistols, so I stand to be corrected, but I really think this would be a big
mistake.
Posted by Chuck Marsh on October 01, 2001 at 23:42:06:
Hello
Warren,
Crossman uses oil in with their Co2 in the 12g cartridges. I have
three Tau guns and have used WD 40 on the guns before with no ill effects. I
have 2 200's and one 7. The advice I suggested was what I have used myself.
Regards Chuck Marsh
Posted by Warren on October 02, 2001 at 10:10:44:
I understand what
you're saying, and I don't doubt that you've had no problems so far.
My
family was (and still is I guess) the TAU dealer for Australia, and I had to re
seal a bunch of them over a four year period. Pistols only, I think there were
less than half a dozen 200s in the country. And it was the fact that some CO2
powerlets do have an oil additive that encouraged many shooters to squirt some
WD40 or something similar up into the gas reservoir.
The problem is that oil
will not generally compress to nothing. If you get a coating of it on the
neoprene seal, eventually it will build to a point where the oil will prevent
the valve from sealing, and you will get gas bypass. It can also make either
sealing surface sticky enough to pick up any tiny particle and cause a slow
leak. The problem was then compounded by a home gunsmith trying to remove the
sealing ring and doing lots of damage, which is the real reason I'm a little
sensitive about TAUs in general.
Oil may be fine in Crosmans - heck, Daisy
suggests using motor oil in their pneumatic air rifles! European manufacturers
would have a fit - could you imagine what FWB would say about using SAE30 inside
a 603?
But the TAU system is extremely simple, there's no complicated
regulation system, just a valve with a light spring to hold it closed when there
is no gas, and a hammer that is released by the trigger sear that hits the valve
from the front to release a charge of gas through the chamber and down the
barrel. The only place it can stick is where the valve body sits in front of the
gas chamber, and unless it's rusted there or been poorly machined at the
factory, it should move freely in its housing. The hammer spring maintains
pressure on the valve when it's not cocked, which is why you cock the gun before
trying to fill it - otherwise it's possible that the bypass might hold the valve
open rather than the gas pressure seal off the gas chamber - ie you might lose a
bunch of gas.
Anyway, nothing personal Chuck, I hope I've explained why I'm
so against the use of oil in TAUs - I believe that in time you'll have sealing
problems, which will be easy to fix (clean off the sealing surfaces). If you
don't, that's fine - it's not that WD40 can do any HARM, it's just that when it
causes problems many people don't recognize it and look to other things that
should be left alone.
Posted by Chuck Marsh on October 02, 2001 at 13:18:10:
Thank You Warren
for the explanation of your experiences with Tau. The Two Tau 200's that I own
have not been used for a year now. They are in my gun vault. The only problems
that I had with them was the breach seal being worn from use and the o-ring seal
for the reservoir being damaged by being taken off and on while saturated with
Co2.
Because of the temperature effect on Co2 I have since went with Anschutz
2002CA which I shoot in Benchrest 50.
I am going to take the two Tau's out of
the vault and see how they doing now after setting up for a year. I felt that
The Tau mentioned had a poppet valve problem. So suggested what I had tried. But
after all the input from everyone he probably will not use a petroleum
lub.
Thanks again for taking the time to give us the benifit of your
experience.
Regards Chuck Marsh
Posted by Brent on October 01, 2001 at 19:07:11:
I had the same problem
with the Tau 200. It was very frustrating, but there is a lever that works
against the trigger (poor terminology but it will have to do for now). This
piece is muzzle-ward of the trigger. Anyway, on my rifle it managed to just
touch the wood of the stock after I screwed down a cap on the 12 g bulb causing
it to torque very slightly and not return under spring tension to its normal
position. The result is I emptied 5 bulbs before this dim bulb figured out the
problem.
In the end, be sure that all trigger mechanisms work as they are
supposed to IN THE STOCK.
Email me if you need better instructions - gotta
run for lecture.
Brent
Posted by TCooper on October 01, 2001 at 23:47:27:
The problem sounds like
it could be with the valve seal where the stem seats(white seal). I would try
and dry the seal off with a q-tip or something. Wrong oils will prevent a good
seal at this point.
The wrong oils will damage this seal. Lubes like WD40
will eat rubber seals. Only use a lube such as pellegun oil or "secret sauce"
because these lubes are rubber friendly. Try it dry first. Another possibility
is a damaged valve return spring. If this spring breaks or is bent then the
valve will not shut completely.
I think you are going to have to do some
disassembly to find the problem.
Tim at Mac-1 is knowledgeable on these
guns.
HTH,
Todd
Posted by Mark Rogers on October 02, 2001 at 23:55:30:
Thanks for all the
input! I took Warren's advice and he was correct. Seating the valve and making
sure that the seal was dry was the cure to the problem. Thanks to all.
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