So I've had it apart before and it seems pretty straight forward. You guys have been very helpful in the past on the 109 quirks. I have a 108 that has a persistent bubbling problem. Lds that serviced it said he cranked it all the way down therefore it still bubbles. One small bubble about every 3-5 seconds. Likely a small fizz from the seat. Anyway, does anyone have the schematic on the 108. Are there any tricks that I should know about?
Sp 108
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Rich Keller
Contributor
Sounds like you need to replace the seat.
That did not turn out too well, I can email it to you if you like.
That did not turn out too well, I can email it to you if you like.
Sure, I'd like that andywolfcpa@gmail.com. Funny thing is it worked great until the service and seat replacement. Anyway, I really need to start doing these myself.
R
redacted
Guest
Time to take a good look at the orifice. If it is an early model with a fixed orifice, then it will probably require a new housing if the orifice knife edge is damaged. Newer models use a replaceable orifice which are easier to replace but use an o-ring that could produce the symptom you describe.
1) The seat has two useable sides and can be flipped.
2) When new, the brass orifices used in the 108 and 109 are sharp enough to damage the seat, so it's a good idea to depress the purge button to lift the seat off the orifice when making adjustments to the orifice depth.
3) The 108, unlike the 109, is a dual adjustment second stage. The orifice position can be adjusted to increase/decrease spring pressure (assuming you leave adequate slack in the lever), but the nut on the outside of the lever and stem needs to be moved out/in to first create the required slack and then re-set the lever height once the spring pressure is set.
4) Generally speaking, cranking the orifice all the way down will increase spring pressure, but it will also lower the lever to the point where the valve will lack adequate working range and will deliver inadequate gas.
5) You can achieve the same level of dysfunction by screwing the lever adjustment nut out to increase spring pressure slightly, but then you'll have a loose, sloppy lever.
6) Assuming new seats are the same size as old seats, replacing the seat and making a minor adjustment to the orifice will usually work, so there are probably techs out there that have never developed a feel for how a two adjustment reg works with a seat of different height.
That could be the problem here if the Scubapro seat was replaced with a generic seat that was slightly thicker, and then not properly re-adjusted to accommodate the higher seat height on the stem.
7) The small o-ring around the adjustable orifice is a smaller than normal size on older 108s and 109s and is often ignored at annual service. I've had regs come in with the older red o-rings that have not been used in at least a decade (and only had a 5 year shelf life). They get dry and crispy and then will leak totally independent of the valve itself.
8) The orifice itself can be nicked on the knife edge and if it can't be touched up, it will need to be replaced. You should be able to feel any nick on the end of your finger nail, even if you can't see it.
2) When new, the brass orifices used in the 108 and 109 are sharp enough to damage the seat, so it's a good idea to depress the purge button to lift the seat off the orifice when making adjustments to the orifice depth.
3) The 108, unlike the 109, is a dual adjustment second stage. The orifice position can be adjusted to increase/decrease spring pressure (assuming you leave adequate slack in the lever), but the nut on the outside of the lever and stem needs to be moved out/in to first create the required slack and then re-set the lever height once the spring pressure is set.
4) Generally speaking, cranking the orifice all the way down will increase spring pressure, but it will also lower the lever to the point where the valve will lack adequate working range and will deliver inadequate gas.
5) You can achieve the same level of dysfunction by screwing the lever adjustment nut out to increase spring pressure slightly, but then you'll have a loose, sloppy lever.
6) Assuming new seats are the same size as old seats, replacing the seat and making a minor adjustment to the orifice will usually work, so there are probably techs out there that have never developed a feel for how a two adjustment reg works with a seat of different height.
That could be the problem here if the Scubapro seat was replaced with a generic seat that was slightly thicker, and then not properly re-adjusted to accommodate the higher seat height on the stem.
7) The small o-ring around the adjustable orifice is a smaller than normal size on older 108s and 109s and is often ignored at annual service. I've had regs come in with the older red o-rings that have not been used in at least a decade (and only had a 5 year shelf life). They get dry and crispy and then will leak totally independent of the valve itself.
8) The orifice itself can be nicked on the knife edge and if it can't be touched up, it will need to be replaced. You should be able to feel any nick on the end of your finger nail, even if you can't see it.
Zung
Contributor
It's about time you take your destiny into your own hands. DA Aquamaster has posted a comprehensive service manual here. I'd suggest you go through it carefully and post any questions you might still have.
And please post some pics of the innards so we can determine if it's a 108 (no orifice) or a 080 (with orifice).
And please post some pics of the innards so we can determine if it's a 108 (no orifice) or a 080 (with orifice).
Well I guess I'm deep into the dark side now. I am on an iPad and can't figure out how to post pictures. Anyway, pulled the orifice (yes it's removable) and found an old red o ring ready to fall apart. Found a o ring of aprox size in a kit I have for the air II I never did.. (different thread) then I went to flip the seat and found it engraved on both sides. Mind you I had it serviced in march used it once (in a pool) took it back because of this problem and got it back still not working properly. Ok back on subject. Replaced seat, reassembled. I've spent a while adjusting everything. Oh ya, I put it on a tank with 600 lbs switched from the mk 5 to my mk 3 (I had a flooded SPG on the 5). And have it to the point that it's cracking at about 1.5 in but not shutting down fully till I bang it in my hand a couple times. I'm guessing that's a lever issue and will take the cover off again and back the lever down a touch. After I get it dialed in with the low tank I'll toss it on another tank with 2400 lbs. (I only have lp steel tanks at home)
---------- Post Merged at 10:46 PM ---------- Previous Post was at 09:53 PM ----------
I dont know if I'm doing something wrong here, cracks right about when the rubber of the mouthpiece hits the water. I figure that to be about 1.7 inches any looser and it's free flowing dry. Feels better than before however and it's not bubbling anymore.
---------- Post Merged at 10:51 PM ---------- Previous Post was at 09:53 PM ----------
Rich,
I can't wait to get those specs in a legible form. The o ring I used seemed pretty tight and may not be spec.
And thanks to all for your help. Especially DA and the thread that Zung linked. When I was searching for a thread I was searching 108 not R108...
---------- Post Merged at 10:46 PM ---------- Previous Post was at 09:53 PM ----------
I dont know if I'm doing something wrong here, cracks right about when the rubber of the mouthpiece hits the water. I figure that to be about 1.7 inches any looser and it's free flowing dry. Feels better than before however and it's not bubbling anymore.
---------- Post Merged at 10:51 PM ---------- Previous Post was at 09:53 PM ----------
Rich,
I can't wait to get those specs in a legible form. The o ring I used seemed pretty tight and may not be spec.
And thanks to all for your help. Especially DA and the thread that Zung linked. When I was searching for a thread I was searching 108 not R108...
Last edited:
halocline
Contributor
I suspect that the best size o-ring for the orifice is a 902. Those red ones do get very crispy, and they seem to be a bit smaller than a standard 010. I have two 108s, one has an adjustable orifice and one doesn't. Surprisingly they perform about the same, which is pretty well.
I think the trick with the adjustable orifice models is to get the orifice adjusted as well as possible, then do the lever height. (as DA Aquamaster said) There's a really good description of the adjustment procedure in the Vance Harlow book.
I think the trick with the adjustable orifice models is to get the orifice adjusted as well as possible, then do the lever height. (as DA Aquamaster said) There's a really good description of the adjustment procedure in the Vance Harlow book.
Just a thought here. Regarding mk3 108 Is there a din kit that can be installed without couv whittling on it? And are there parts available to make it o2 clean.? It's so compact I just had a thought to turn it into a deco rig.
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