Catman Posted February 7, 2008 Report Share Posted February 7, 2008 Well it has to be said that these King Arms CNC grenades are a pain. Problem is their so cheap they're worth a bit of hassle. I seen a few people on these forums having issues with them so here's a walkthrough on how to get your grenades working properly. Fixing the Design Flaw First of we should fix the major flaw in their design. The top of the grenade leaks, you might think the gas is leaking through the fill valve but chances are it's not. Unscrew the top cap of the grenade, you can use something like a needle nose pliers for this. The grenade with the top cap removed: The problem is the o-ring in this top cap piece, it doesn't form the best of seals. Now you have a choice on fixing this problem. You can either install a second o-ring or you can take that o-ring off and move it onto the thread. Option #1 2 o-ring method (if you want to be doubly sure it won't leak): Install a 2nd o-ring as so: Option #2 Moving the o-ring Method (note this is pictured on a different grenade!): Remove the o-ring from it's groove and place it on the thread as pictured: Screw it back in tight and you're done with that bit Link to post Share on other sites
Catman Posted February 7, 2008 Author Report Share Posted February 7, 2008 Fixing the Firing Mech from leaking Sometimes you'll gas us your grenade only to hear gas leaking down the barrels. So here's how to fix that... If you unscrew the grenade, you'll get these bits fall out. Make sure you have all 8 ball bearings Now remove the o-ring from the valve unit (mines black but on other KA grenades the piece can be silver). The o-ring can leak because it's slightly too small. Having tried various methods (such as PTFE tape under the o-ring) the best method unfortunately takes a few days to work. You'll need some Brake & clutch fluid or steering fluid for cars. This week I have mainly be using this: (Get an empty jar from the kitchen and pour some of the fluid into it. Blatant labelling is optional ) Drop your o-ring into the jar and leave it there for a few days to a week. The fluid will penetrate the o-ring and cause it to swell slightly. Some automotive fluids work better than others (the stuff I got isn't the best) so keep an eye on the o-ring each day. If it swells too much you may have problems with it fitting. On the left is an o-ring before having it's bath, the one on the right has been soaking for over a week. You can see that it's slightly increased in width. It's also better formed and the rubber is much healthier. Stick the o-ring back onto the valve piece and give it some drops of silicone oil (not the spray stuff). Putting it back together Ok now if you don't already know, here it is a again. Get some grease (anything will do as long as it's NOT petroleum based) and gunk up the 4 little holes on the valve. Put 2 ball bearings in each of the holes. The grease will hold the bearings in place and make it much easier to handle Put the valve onto the grenade like so: Now sit the striker and spring on top like this: Drop the casing on the top and screw it in a few turns: The striker will be out of position, so with a screwdriver just nudge it into the centre of the hole: Once that's in position screw it all the way. Link to post Share on other sites
Catman Posted February 7, 2008 Author Report Share Posted February 7, 2008 Fixing the Fill-Valve If you think the fill-valve is leaking it's usually down to a simple issue. But before you start to use these grenades lots you should run through these little steps to make sure it stays trouble free. Now this you can apply to all GBBs etc. The fill-valves are identical in design, the threading etc maybe different on a GBB but it all works in the same way. Unscrew the fill-valve from the grenade (or mag) using a decent sized screwdriver, you want one that fits nicely or quite likely damage the head as they're made out of soft brass. On removing the fill-valve you may look more like the valve on the left than on the right: The bottom of the fill-valve likes to unscrew itself over time, again you'll find this in GBBs as well. Now if we unscrew the whole fill-vale we have this: The bit with the tiny o-ring on it is the valve. Remove the o-ring as carefully as possible. The tiny hole in the valve can sometimes have a burr on it, this will slash the o-ring up to a point where it's not able to hold gas. So get a small file and gently go over the hole to remove any burrs. Inspect the o-ring and make sure it's well formed and all intact. If it's damaged you may have to replace it (sourcing such small o-rings can be a pain). Again you can try giving it an o-ring bath for a few days or week, that may well swell the rubber enough to make up for the damage. Give the o-ring some silicone oil, put it back onto the valve and reassemble, don't screw the bottom of the fill-valve all the way in just yet. Put a tiny (extremely tiny!) dab of thread locker on the thread. If you put too much it'll get inside to the valve and potentially cause problems. Screw the fill-valve back into the grenade. Do not be aggressive in screwing it in, the valve does not need to be in tight. If you try to screw it in too tight you'll rip the fill-valve's head off and it'll be destroyed. Link to post Share on other sites
Catman Posted February 7, 2008 Author Report Share Posted February 7, 2008 Using the Grenade These grenades are very simple to use. To reset the valve unscrew the base a few turns. You'll hear a small click as the valve resets. Screw back together and charge with gas. The Golden Rule: fill with gas BEFORE you put in BBs When filling with gas the valve can slip resulting in it firing. One thing I've noticed: it's best to refill the grenades with gas as soon as possible after firing. Even if it's just a small squirt of gas, as long as there's some pressure in there to keep the o-rings expanded. For storage; also keep the grenades charged with gas. If they're not going to be used for longer than a week give them a full fill of gas. If there are still some leaks they will be minute and take a long time for the grenade to loose all it's gas. Link to post Share on other sites
sniperjarman Posted February 7, 2008 Report Share Posted February 7, 2008 Marry me. That way you can live here and sort out all my airsofting problems! Link to post Share on other sites
galactica Posted February 7, 2008 Report Share Posted February 7, 2008 Catman, you are some kind of golden god. Link to post Share on other sites
sniperjarman Posted February 7, 2008 Report Share Posted February 7, 2008 Right, taken it apart, and the o ring on the valve (the miniture one) is destroyed to hell. And its a bloody new grenade!!!! Do you know where you can buy these new? I mean its like a 1milimetre oring?! Link to post Share on other sites
sniperjarman Posted February 7, 2008 Report Share Posted February 7, 2008 No worries, found a site. Min order of 20 pieces tho! lol. So i'm gonna order 20 of 3 sizes. So if anyone else needs one, PM me and you can have some for free!! In fact what I'm gonna do, is order 20 of each size O-ring in this type of grenade. So PM if you wanna but a complets set of O-rings for this grenade. I'll say £3 a set posted? Cheaper than any airsoft site charges! Link to post Share on other sites
Catman Posted February 7, 2008 Author Report Share Posted February 7, 2008 I bought a set off ebay. http://cgi.ebay.co.uk/200-Pc-Black-Rubber-...1QQcmdZViewItem http://cgi.ebay.co.uk/Boxed-200-assorted-r...1QQcmdZViewItem I didn't get my set from either of these people though. It comes with 35 3x1mm o-rings. Now these are a fraction smaller than the one in the fill-valves. I believe those are 3x1.15mm but a week in the o-ring bath should swell those 3x1's to fit nicely. Saying that I have successfully used 3x1's straight out the box, sometimes the valve leaks a little but it's cured by putting your finger over the valve and pressing down to create a quick seal. Link to post Share on other sites
sniperjarman Posted February 7, 2008 Report Share Posted February 7, 2008 Cheers for the links. This thread needs to be stickied. Link to post Share on other sites
Edmiles Posted February 7, 2008 Report Share Posted February 7, 2008 Well firstly, great article as usual Mr. Catman. But I would like to add, that the the first problem (the design flaw) seems to only be present in the higher capacity versions as you have. The 60rounders which I have do not suffer from this problem. I must also back you up on checking the fill valves straight away! My grenades are still quite new, only taken them to the field once! Yet one of them had worked itself lose, I assume it was already lose to a certain degree, but it had caused leaking from the fill valve until I tightened it back up. Link to post Share on other sites
Catman Posted February 7, 2008 Author Report Share Posted February 7, 2008 I got 6 of them, 3 of the large 190 odd round and 3 of the 120 round ones. Not all of them leaked from the top cap straight away, In fact I think one never leaked but I went and pre-emptively fixed it. My worst fear is being in the field, going to fire only to find all the gas has leaked out - it's happened to me on a couple of occasions and it's not fun, not when you've had 3 people bunched together that you could have gotten with one grenade Definitely: Anyone who buys these grenades should check out and file down the hole on the fill-valve before it wrecks the o-ring. Link to post Share on other sites
Rapier Posted February 7, 2008 Report Share Posted February 7, 2008 Catman, can you give sizes for all the o-rings? Link to post Share on other sites
Eugene_Stoner Posted February 8, 2008 Report Share Posted February 8, 2008 I was thinking of buying 3 of these in a week or so, think i may have changed my mind now, i hate having to fix things that shouldnt have to be fixed.. Link to post Share on other sites
galactica Posted February 8, 2008 Report Share Posted February 8, 2008 there are no maintenance-free gas grenades. Link to post Share on other sites
Eugene_Stoner Posted February 8, 2008 Report Share Posted February 8, 2008 Very true, at least theres a handy guide, pretty simple stuff really. Link to post Share on other sites
Catman Posted March 15, 2008 Author Report Share Posted March 15, 2008 Lots of people been asking me for the sizes of the o-ring. So here's a nice little break down of the sizes, now the measurements could be off by a few fractions but anything roughly those sizes should work. Remember you can soak o-ring in steering fluid to make them a little larger if they're too small. btw if the steering fluid expands your o-ring too much just take the o-ring out and let it dry off some where for a few hours (on top of something warm is good - I wouldn't recommend a radiator). Link to post Share on other sites
chownsy Posted March 15, 2008 Report Share Posted March 15, 2008 i put my o-rings on top of a radiator after my brake fluid expanded it too much as you know (many thanks for your help again) i coated it in a small amount of silicon oil and then put it on a hot radiator, or cold and it was set to come on in the morning,( we got a twin radiator and the bracing is perfect for putting the o-rings on as it dont ge as hot as the main radiator part but warm enough to dry them out over night/morning) it gradually warmed up and when i got up it had shrunk slightly and not cracked cause was still moist from the silicon oil on it. Hope this helps a little more too. Link to post Share on other sites
Catman Posted March 15, 2008 Author Report Share Posted March 15, 2008 cheers Just didn't want people putting their o-rings on top of radiators then coming back to them some time later to find they'd melted to some degree Link to post Share on other sites
chownsy Posted March 15, 2008 Report Share Posted March 15, 2008 cheers Just didn't want people putting their o-rings on top of radiators then coming back to them some time later to find they'd melted to some degree about 3 hours maximum, but that included the time the radiator took to warm up too. make sure there lightly coated with silicon oil to stop them drying out Link to post Share on other sites
Brandon Grave Posted March 30, 2008 Report Share Posted March 30, 2008 Catman, Do u know if the fill valves are the same size as the ones on the magazine of a tanio koba usp. The fill valve that I have will not hold any gas. Of course i will try the silicone oil trick. But as far as replacing the o-ring, I was wondering if it should be close the 3x1.15mm? I love the fact that I found some kind of answers though. Thanks Link to post Share on other sites
Catman Posted March 30, 2008 Author Report Share Posted March 30, 2008 Hello, Thanks I can't say for sure but that will most likely work, I've found the internals of fill-valves to be pretty universal. It's usually the threading and head that vary. If you find it still leaks with a brand new o-ring then stick it in the "o-ring bath" for a bit (depending how aggressive the fluid is at swelling o-rings). Link to post Share on other sites
filipinofreak Posted September 23, 2008 Report Share Posted September 23, 2008 Lots of people been asking me for the sizes of the o-ring. So here's a nice little break down of the sizes, now the measurements could be off by a few fractions but anything roughly those sizes should work. Are your diameter measurements inside or outside diameters? I'm going to take a chance and buy o-rings to have around for replacements. I can only buy in packs of 100 and can't afford too much variety to experiment with. I can get also get different widths. Do you feel picking a width 0.5mm thicker will decrease the need to fatten up the o-rings? Or will it be too big? Thanks for all the great information on these grenades. Saved my friends and I a lot of problems Link to post Share on other sites
Catman Posted October 10, 2008 Author Report Share Posted October 10, 2008 Sorry for the (massively) late reply, the o-ring sizes I mention are OD. I don;t think you'll get away with using o-rings that are 0.5mm fatter. 0.25mm yeah but I doubt you'll have much luck with 0.5mm Link to post Share on other sites
Jinx Posted December 18, 2008 Report Share Posted December 18, 2008 Great article superb info very disappointed in my first KA 60rnd shell with 3x 190's on the way. But have now carried out the fixes and played this weekend faultless, and it was chilly not good for gas gizmo's. Cant wait for the warmer weather. Big thanks Catman Cheers Jinx Link to post Share on other sites
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