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Old 10-04-2012, 01:46 AM   #57 (permalink)
Sidewinder Hoarder
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Join Date: Dec 2010
Location: Fascist Valley

Originally Posted by barkingspider View Post
For those who have been educated on this thread about the workings, or lack there of, with Metadyne I would urge you to form your own opinion. I for one know a little more about the dealings of this company and those behind the scenes. I think the story and misconceptions about issues with this marker are a little sharp. Without going into a lot of detail, if you're looking to have issues with the marker addressed just give Brian a email. SEND THEM TO:

He will respond to you, just keep in mind that he is a solo show, which means he isn't just waiting at his desk for your email to roll in. Be reasonable and respectful and he will take care of your needs by treat you well.

From time to time I come out the shadows to defend Metadyne and the extremely small production he has. I have no affiliation to him or his company other than the respect I have gained over the years for the products he makes, but more importantly how he stands behind the items and how he always will make things right. I throw his out as something to think about before drawing a skewed perception based upon misunderstandings and half truths.

The new piston seem to work great! I have it in two of my markers

I know that I stand as a target for those who feel I have altered agendas, but I thought I would try and promote the concept of giving them, Metadyne, the benefit of the doubt in a bumpy journey for all parties involved. Just my to cents and now I shall retract into the shadows again..........

Before I begin, I just want to recap an earlier fix for the Thumper that joedirt and I (and others) seem to have discovered independently of one another: Use an inline reg with you Thumper!

[ALERT]The plausibility of offering a Thumper Specific O-Ring kit is being researched. Please visit this thread,, and give you feedback on the idea. If and when they become available I'll update this post with the info on where to get them and how much they will cost (won't be much). Hopefully we'll have different durometers to choose from (70-80-90), maybe even different materials! [/ALERT]

What you need:

It'll work with either HPA or CO2. A remote or a/s setup should be used with CO2 to keep liquid from fowling the seals. You will need a good reg that has an adjustable output capable of a reliable 200-300psi. Never set your inline reg to more than 300psi! This is the operating limit of the actuating valve within the Thumper. Jd had great success using an old stock used WGP reg (of the older internally adjustable variety). I believe he set his inline reg to 300psi to keep the Thumper's internal reg from spiking over the actuating valve's pressure limit, and using the Thumper's internal reg to fine tune velocity. I have had great success using an AKA 2L+Dual (over 8k rounds now shot without problems of any kind) set to 250-280psi. I decided to disable my Thumper's internal reg completely, relying on the 2L for velocity adjustment. (1)

After a couple months of using the WGP reg in conjunction with the Thumper's internal reg, Jd mentioned he'd started having problems. Accordingly, unless it's been working out of the box (some people have Thumpers that work great without any mods of any kind!) I strongly suggest disabling your Thumper's internal reg and instead relying completely on an inline reg to fine tune velocity. REMEMBER: Never set the inline reg to over 300psi! That is, unless you already know your internal reg works. If you do, and the internal reg fails on you, which often seems to happen, you end up with a fussy gun at best and a broken main piston/valve at worst. In other words - A very sad panda. (2)

Adding an inline reg is an outstanding solution to keeping your Thumper up and running. This is described in detail below. It is also a good idea to replace all your Thumper's o-rings out of the box, as a good number of them seem to have come with poor quality seals from the factory ($5 dollars is a small price to pay for reliability). Many of the correct o-rings can be found in an EGO o-ring kit. If you want a list of all the necessary o-ring sizes or a good source, shoot me a pm. If you can, try to get 80 or 90 durometer o-rings. I have only tried using 70 durometer, but Woouulf speculates that the higher durometer might help a whole lot. From what I have experienced that seems absolutely right.

The last, most important step? Enjoy kicking *** with your awesome working Thumper! (3)

Falling in Love With Your Thumper, All Over Again:
A Few Easy Fixes

90% of people who have bought the Metadyne Thumper (Gen 1 and 2) seem to have had problems. Something goes wrong and they don't fire properly. The actuating valve breaks down or the main valve/piston fails, splitting in half at the front most o-ring groove. I long hypothesized that the problem was related to flaws in the design or manufacturing of the gun's internal reg system.

Whatever it was, it seems to have to do with the internal reg. For example, hearing about actuating valves failing one after another pointed to their being over pressurized. Their limit is 300psi. Same with the bolt breaking at the first o-ring groove, despite multiple redesigns (the most current design is supposed to fix this issue, but you are required to send your marker into Metadyne as machine work is required and isn't a drop in upgrade). New o-rings seems to help the matter, but before long I heard that this didn't solve the matter. Some also have had success with polishing the reg piston/valve, but it still didn't guarantee a working system. (4)

Now, I want to be clear: I do not believe these are the result of simply design or conceptual flaws. The design of the internal reg is ingenious, as is the cocking system and main valve. However I do believe they are not using the best possible methods of manufacturing or quality control, such as polishing the reg piston/valve and its housing in house or using the best quality o-rings (two thing it often needs, I might add, due to the high tolerances required by the internal reg's design). (5)

A good number of Thumper owners (five I know of) have never had problems, other than the occasional pinched ball (this seems to be solved by shaving a little off to round off the tip of the detent). I do wish I could have just taken my Thumper out of the box, thrown a tube of paint in, screw on a 12g, adjust the internal reg to 280fps and hit the ground running. I still dream that one day I will have the pleasure. (6)

After first hearing about the Thumper a year ago, I waited a long time to buy one. I had hoped that the flaws of the earlier models would be addressed as the gun was technically at the time still a prototype. Some were, such as the wider detent insert to decrease pinching. However, the more time when on, I still heard negative feedback regarding reliability. This seemed to wain somewhat when the Gen 2 was released. Although the situation still wasn't ideal, I just couldn't wait any longer and ended up buying my (first) Thumper. (7)

I did not play with my Thumper for one or two months after I got it. I was again hoping Metadyne or someone would figure out a way to somehow fix all of the gun's potential for problems awaiting me when I aired it up for the first time. Thankfully, with the help of many folks from MCB, I have been able to avoid any discomfort and take fully advantage of a wicked, somewhat radical pump.

As I was saying, I had begun to suspect from what I was seeing and reading on here that the internal reg was the main culprit. One day, with my confidence level high and with a very positive attitude, I replaced all her o-rings, lubed them with a tiny bit of magnalube, disabled her internal reg, slapped my 2L on her and aired her up for the first time. (8)

No problems at all! I had already set my 2L's output to 250psi, and had to adjust it up to about 275psi to achieve 290fps. A quarter case later (500-600 shots) and I was walking around with a **** eating grin smeared across my mug for the rest of the day. Since then I've purchased another Thumper, one that had broken down with it's previous owner. I did the same things I did to my first one, replacing all o-rings, properly lubing her up and adding a good lp inline reg (this time an AKA Sidewinder also set around 260psi).

Once again, no problems whatsoever after having put 2-3k+ rounds through her. As soon as I can afford it (although the list of guns to buy is rather long right now ) I'm going to buy myself another Thumper (Gen 3 maybe?). I am so excited, if somewhat jaded, to try the new main valve/piston design. With all the horror stories about sending Thumpers into Metadyne to get upgraded and not hearing anything for six-plus months, I'm obviously not too keen on sending one in for the upgrade. Yes, I am somewhat controlling when it comes to my babies... (9)

In terms of maintenance, I service each one every 500 or so shots. I've used HPA on both Thumpers, although I'd like to try an a/s CO2 with a Stab and Sidewinder or 2L sometime. I think Jd had more success using properly reg'd a/s CO2 than he did with HPA. Anyways, I've done a bit of thinking since getting my first Thumper months and months ago and the following (along with the above) are some of my thoughts. (10)

A Good Regulator:
The Solution?

To better utilize my inline reg idea, I have "turned off" the internal reg in each of my Thumpers. I achieved this by inserting a little delrin spacer where the reg piston's spring normally sits and removed the middle o-ring on the reg piston. The spacer is to stop the reg piston from any movement or travel that would potentially allow the reg piston to do its job. Removing the middle o-ring also facilitates that goal. This is actually the easiest way to disable the reg, but you need to make sure you have the velocity adjustment screw tightened against the spring as much as possible if you're not using an insert (just don't overdo it so it gets stripped!). (11)

NOTE: Do not removed any other o-ring than the middle one. If you do remove one of the o-rings on either end of the reg piston you will create a leak. Other than those two o-rings, there isn't anything to seal either end of the reg piston's housing. (12)

Here's what the reg piston actually looks like:

The following would have been so much easier and cleaner if I had some sort of CAD program on this computer, but, alas, Paint works.

The diagram on the left illustrates the position of the reg piston when marker is NOT PRESSURIZED. The one of the right illustrates what the piston looks like when the marker IS pressurized and the reg piston is at equilibrium under pressure.

Now, it should be more obvious, how replacing the spring with an insert would disable the internal reg. And why removing the middle o-ring would do the same. AND why you don't want to remove the o-ring on either end of the reg piston. You want the reg piston from moving, thus keeping it from closing off the input OR you want the air to be able to flow unrestricted between the input and output by removing the middle seal. (13)

Last Thoughts on Internal Reg:
So Much Potential

After a bit more thought with some overpriced coffe this morning and some cheap wine this evening, I've come to the conclusion that, indeed, with quality o-rings (of the proper durometer/material/size), a good polish and a more reasonable input pressure (say, less than 600psi, but not less than 350psi absolute min - keep in mind the marker needs 200-300psi to operate, or at least this seems to be the case) - that the internal reg could work quite well. (e1)

Here is a link to my original post about this in that other Thumper thread:


Miscellaneous Info:
O-Ring List and Further Solutions to Other Potential Problems

Problem (1)
-Problem cocking the marker? Make sure the cocking rods are even in the back block thing and the breach slide at the front. Use a hammer to tap them back into the cocking back block or breach slide. (Thanks Woouulf!)

Problem (2)
-Thumper auto-triggering whenever you go to cock it? There is a spring in the trigger assembly that acts as its guide. Clip a couple coils off it, one at a time, so you know when to stop (either that or have a backup to use if you cut yours too short). (Thanks [again]Woouulf!)

-Correct O-Ring Sizes: I've had luck using 70 durometer o-rings but it may be the case that 80 or 90 durometer orings work even better, particularly w/o the use of an inline reg. Here is a complete list of the o-ring sizes required:

Main Valve/Piston: 109, 006 (x2), 112
Internal Regulator Valve/Piston: 006 (x2), 012
Actuating Valve: 010 (x2)
Breech Cylinder: 1x15, 021
12gram Adapter: 016, 015
V-ASA: 1x15
Under 3 Set Screws: 1x4
Trigger Frame Safety: 006

So that would be total of:

5x: 006
2x: 010
1x: 012
1x: 015
1x: 016
1x: 021
1x: 109
1x: 112
2x: 1x15
3x: 1x*

*Not really necessary as they're used to seal static setscrews/air passageways, and you probably won't need to replace these unless you're run a bunch of liquid CO2 or Drano(C) through your Thumper...
**Thank you red army.


And finally... This wouldn't be complete with a general but all important reminder regarding maintenance:
-ALWAYS make sure to check o-rings when cleaning or servicing the gun to make sure they're still in good condition. This is true especially when your Thumper is running on it's original from Metadyne seals or have recently replace the original seals with new ones. Remember to use a good lube such as magnalube.
-Oil type liquid lubricants are frowned upon, as the manufacturers of the actuating valve state that it is meant to run dry. Some folks haven't had any problems with using this, but you do run the risk of compromising your actuating valve, forcing you to replace it completely ($5-20 I think depending on where you get it).
-This last section will be updated as I people share their positive experiences fixing, tweaking and/or upgrading. Speaking of it, I want to thank Woouulf, Joedirt and everyone else who has contributed the Thumper achieving it's rightful destiny. What destiny you ask? AWESOMENESS!



Who wants to get the Newest Beefiest Piston yet for the Thumper? You do have to send your Thumper (or rather it's main body section) in to Metadyne to get it upgraded. If you don't mind a little lag time and are patient by nature (or want to learn) this is a great opportunity to avoid having to use an inline reg to prevent your Thumper from breaking down. That means you can run it off 12g and play stock class without any worries, like it was intended! Yippee!!!

Contact Metadyne (Brian):

Thanks CP


Disclaimer: I'm not perfect. If this isn't how the reg piston works or I don't have the right o-ring sizes posted, well, I hope someone will point that out.

Last edited by toymachine; 11-01-2012 at 07:50 PM.
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