I need help! RT On/Off in Classic Valve

[xero28]

I have an RT on/off in a classic valve, I just bought it last week (the on/off, I've had the valve for about 13 years). I dropped it in and the valve would not charge, and when I pull the trigger, it just feels "mushy", no firing. I cranked up the velocity, same thing. I took out the RT and put in the regular on/off, and it started to do the same thing, then after adjusting the velocity in and out a bit, it started to fire.

I am wondering if it has to do with the tank pressure. My regular HP tank is just about empty, so I'm using an old adjustable that can only go up to 500-600 psi (valve is broken somehow). As I understand it, the regular RT valve has to have pretty high pressure to operate? Do I need to have a full tank (over 1000 psi)? Or is that just for the RT and to eliminate shoot down?

Or is it something completely different? I just played about 4 weeks ago and had no problems whatsoever going through 1/2 case.

Any input would be appreciated tremendously as I'm going out again this Saturday. Thanks.

[athomas]

If the valve won't charge and the trigger feels mushy, it is usually an indication that the on-off pin is not opening the airway. Are you sure you are using the proper on-off orings and that you don't have an extra one in there somewhere?

A lower pressure tank may not work if the valve is setup for a level 10 bolt. It should work, but not well if the valve is set up with a level 7 bolt.

[xero28]

I have yet to open up the on/off since I got it and make sure the proper o-rings are there. I've never used an RT before, and from what I've seen on airgun.com, the rings in the on/off should be urethane, not teflon. Am I right. Could it be I just need new o-rings in there? If so, can someone tell me if they have to be urethane, or if buna works. I don't have any place close by that sells urethane.

[xero28]

Am I a moron? I was looking again at the blowups on airgun.com, and I was looking at the RT valve diagram. From what I can tell there is only the small urethane o-ring below the on/off, and the other rings are inside. Does that mean that on my classic I need to take out the power-tube sized o-ring that is below the on/off and just have that small one? Any input would be great. Thanks.

[questionful]

Leave the powertube-sized O-ring in there!! Old RT valves used to have a step in the on/off hole.


Sounds like maybe the on/off just isn't opening. To see if this is the case, air up the gun without the powertube O-ring (the one in your powertube). If there's a big leak, the on/off is open. If not, then it's closed.

If you have calipers, measure the length of the on/off pin and tell us the length. It should be .750".

If you find there's nothing wrong with your on/off assembly, I would just shave the pin down.

[xero28]

So are you saying that the pin might be .765? And that it should only be .750, nothing more, nothing less?

[questionful]

According to the sticky, yeah, if it came off a RT pro it would be .765". If I were you, I would just shave it down. I just don't know how sure you are that you installed it right? If everything is how it should be and it doesn't fire, I would shave the pin down. But that's up to you, once you take metal off you can't really put it back on, you'd have to buy another pin.

[athomas]

...from what I've seen on airgun.com, the rings in the on/off should be urethane, not teflon. Am I right.

You are correct. The inner oring doesn't work well when it is teflon in a retro pin assembly. Plus, the urethane outer oring is a bit more stiff and holds the inner oring in place better than buna. You can use a quad oring for the top center oring. It can buna. The quad works very well which is why it is used in the emags, although it may exaggerate your problems. The quad o-ring moves the sealing point of the on-off pin down which simulates a longer pin.

[xero28]

According to the sticky, yeah, if it came off a RT pro it would be .765". If I were you, I would just shave it down. I just don't know how sure you are that you installed it right? If everything is how it should be and it doesn't fire, I would shave the pin down. But that's up to you, once you take metal off you can't really put it back on, you'd have to buy another pin.

Thanks for everyone's responses.

As far as I know it is installed correctly. I bought it off of cbr600rr and just dropped it in. Here is the link to the pic from his for sale post.

http://i53.photobucket.com/albums/g51/shock3rd/rtonoff.jpg

I opened up the on/off and everything seems to be in order, although the o-ring inside is quite stiff, but I can't tell if it is teflon or just really small. It just doesn't seem to have the give of urethane. I think you're right questionful, after thinking about it and checking out diagrams and animations, I think it is a long pin and it just needs to be shaved.

And speaking of animations, I found this place last night. I'm sure you've many, if not most of you have seen it, but I thought it was pretty cool.

http://www.zdspb.com/tech/misc/animations.html

[xero28]

I just measured the pin, and it is .750 inches (I just used a ruler, but I'm confident it is accurate). Could it be that there is too much friction on the pin from the o-rings and I just need to lube them a bit? Or could it be the compatibility issue with an older valve. (Is there any difference between an "old" classic and a "new" one?). I will try and fill my HP tank today and get some more pressure on the pin and see if that works.

[flyingpootang]

Generally if you trigger is mushy your tank pressure is to low to operate the valve. If your trigger is to hard/stiff your on/off pin is to long. If your marker goes full auto your on/off is to short. Xvalves operate from 800 and up. Keep in mind that all mags are different. Switching a working valve into a different body and/or rail may or may not work. I would start with getting a full fill on your tank. Make sure your tank is a high pressure out put tank 800 & up. All 4 of my classic valves have RT on/offs with @ .750 pins. All of the triggers are real light and constant. I have 1 classic with a ULT in it and have had no problem with tuning it.......

Edit: Corrected

[Spider-TW]

Also, remember the little gauges on tanks are not precision, possibly +/- 100psi over 1500psi span in a few years on some, and +/- 250 on a 5k gauge. When the pressure gets low and iffy on the bottle, I stop tuning because the on/off may not be under full pressure (and not in it's usual location that we fight to get to the best +/- 0.005 inches).

And like athomas said, with a lvl 10 bolt that is necessarily sensitive to pressure, it's pointless to troubleshoot with low supply pressure.

[athomas]

If your trigger is to hard/stiff your on/off pin is to short. If your marker goes full auto your on/off is to long. .....

I think you have that backwards.

A short pin allows air to flow sooner with the sear tip having less contact with the bolt. It takes less motion in each direction during the trigger pull and release. Less motion means it is easier to achieve full auto. If the on-off pin is too long, it never opens the airway to recharge the front chamber. You are always pulling against the force on the top of the pin because that is where the pressure is exerted. It this full force over the entire trigger pull that gives it the mushy feel.

[flyingpootang]

I think you have that backwards.

A short pin allows air to flow sooner with the sear tip having less contact with the bolt. It takes less motion in each direction during the trigger pull and release. Less motion means it is easier to achieve full auto. If the on-off pin is too long, it never opens the airway to recharge the front chamber. You are always pulling against the force on the top of the pin because that is where the pressure is exerted. It this full force over the entire trigger pull that gives it the mushy feel.

Your right it is wrong LOL I wrote this on 2 hours sleep

[athomas]

Your right it is wrong LOL I wrote this on 2 hours sleep

LOL. I've done that one a few times.