New to me MK10+/G250 R109/108

[Eric Sedletzky]

I ‘think’ a current OEM G200 second stage kit works in a 109. However I’m not sure if that’s one in the same as a “duro poppet”.
I have several late model MK5’s - down to three now, and a few 109’s torn down in bags waiting for rubber diaphragm covers to land on me out of the heavens.
I just recently gave away two MK5/109 setups to a fellow diver in need.
One thing I do, and it may give some purists and collectors heartburn, but I drill out the ambient holes a bit on the later MK5’s to make them easier to rinse, since I will never pack them with silicone to make them SPEC. I don’t care about modifications or Frankensteining since I will be using these things until I end up in the big reef in the sky.
I have a way of rinsing them really good and never have a problem. MK5’s are about the easiest thing to work on. The only reg easier are MK2’s.
You do need a piston bullet for sure, and maybe a piston shaft O-ring installer, but many people do without them.
Mk5’s are the ultimate DIY reg, and as far as I’m concerned about as good as Scubapro pistons ever got. The only thing I would change is the brass turret bolt to a stainless bolt. But look at how many MK5’s are out there still with brass bolts and they are still fine. They can’t be over torqued. Oh yeah, you will need an inch lb. Torque wrench too.

 

[Kupu]

I ‘think’ a current OEM G200 second stage kit works in a 109. However I’m not sure if that’s one in the same as a “duro poppet”.

Yes, the current duro poppet kit is #11.109.045 for G200, 109, & M50. It also provides new screws for the 109 cover ring clamps.

A side note... There are a couple versions of the clamps which have different threading and so 109 ring clamp screws are not universal. But the screws can be reused in most cases, and the screws in the kit match a large majority of the 109s I have come across.

 

[dstalsby5]

If you're asking why some shops won't service old regs, it's equal parts marketing, fear of litigation, and ignorance. The marketing aspect is "those old things can't be serviced anymore, here spend $$$ on these new ones". The fear of litigation is a belief that they are at risk if they use anything other than a factory supplied "Service Kit".... even though a duro 90 -10 O-ring is the same whether it was bought in bulk or as part of a kit. The ignorance is that many techs aren't really techs... they are parts swappers. If they don't really understand the gear and just do what book says so because book says so, they won't ever look beyond a factory parts kit or availability of new parts from the manufacturer.
If you're asking who will do servicing on this board, I hesitate to throw names out without checking with them first. If your shop won't work with you, just put up a thread here and I suspect you'll get a number of people willing.
If you're thinking of DIY, for those specific regs I'd look here: https://www.youtube.com/@Vintagedoublehose1964
Bryan did a number of videos going through them step by step (the MK5 and 10 are similar enough that the MK5 video covers it.

Respectfully,

James

My LDS does not service SP. I go to a shop about an 1 1/2 hrs away. They seem good, I just never buy anything from them and have not really built a report with them. Just bring in older gear for them to service. I’m calling them tomorrow to see what they can and will service. I might have to buy the kits on-line but we will see.

 

[dstalsby5]

I am keeping the Mk5, in my mind or read that the mk10 was a better first stage. In truth I care more about being in the water then I do what I am using. I tend to put the cart before the horse at times.

I'm not sure why you are forsaking the MK5. I personally prefer them to MK10s, and yours is one of the later, more desirable MK5s with 5 LP ports and a heavy yoke. I would definitely keep that and service it. You may find that the MK10+ has it's problems. It uses a blunt-edge piston and the MK20-25 seat. The combination was designed to increased airflow but IME they tend to have problems with IP creep. I can't get any of my MK5s to creep even if dive them for years without rebuilding.

Regarding the 2nd stages, you've already received excellent advice, personally I convert my 109s to balanced. Sometimes the older levers work well with the s-wing poppet, sometimes not and it seems to be a bit of a crapshoot in terms of performance. The general issue is that some, not all, of the older levers result in a bit more lever height than the newer 'curly feet' ones. This requires you to tighten the orifice a little more to drop the lever, and the cracking effort increases. I also have found that there is some inconsistency in the springs. I always replace them when I'm rebuilding/converting a 109 or 156 (which is the 'balanced/adjustable' younger brother of the 109). I have spent many pleasant hours fiddling with various levers and spring combinations to get the best performance out these older, classic metal 2nd stages. When you get it right, they are wonderful to dive with, better IMO than the G250. In fact, I've come to the point where I'm only using B/As and 109s in my cave diving, so I have several. (Thanks to a few folks on this forum!) I also use a pair of MK5s in my cave set up and have semi-retired my sealed MK10s. They just don't last as long between rebuilds IME as the MK5.

Bringing an end to this long rambling post, I feel that you have the ideal combination right there; a late model MK5 with a 109. So let your wife use the G250 and let someone else deal with the creepy MK10+.

I'm not sure why you are forsaking the MK5. I personally prefer them to MK10s, and yours is one of the later, more desirable MK5s with 5 LP ports and a heavy yoke. I would definitely keep that and service it. You may find that the MK10+ has it's problems. It uses a blunt-edge piston and the MK20-25 seat. The combination was designed to increased airflow but IME they tend to have problems with IP creep. I can't get any of my MK5s to creep even if dive them for years without rebuilding.

Regarding the 2nd stages, you've already received excellent advice, personally I convert my 109s to balanced. Sometimes the older levers work well with the s-wing poppet, sometimes not and it seems to be a bit of a crapshoot in terms of performance. The general issue is that some, not all, of the older levers result in a bit more lever height than the newer 'curly feet' ones. This requires you to tighten the orifice a little more to drop the lever, and the cracking effort increases. I also have found that there is some inconsistency in the springs. I always replace them when I'm rebuilding/converting a 109 or 156 (which is the 'balanced/adjustable' younger brother of the 109). I have spent many pleasant hours fiddling with various levers and spring combinations to get the best performance out these older, classic metal 2nd stages. When you get it right, they are wonderful to dive with, better IMO than the G250. In fact, I've come to the point where I'm only using B/As and 109s in my cave diving, so I have several. (Thanks to a few folks on this forum!) I also use a pair of MK5s in my cave set up and have semi-retired my sealed MK10s. They just don't last as long between rebuilds IME as the MK5.

Bringing an end to this long rambling post, I feel that you have the ideal combination right there; a late model MK5 with a 109. So let your wife use the G250 and let someone else deal with the creepy MK10+.

 

[dstalsby5]

Yes, the current duro poppet kit is #11.109.045 for G200, 109, & M50. It also provides new screws for the 109 cover ring clamps.

A side note... There are a couple versions of the clamps which have different threading and so 109 ring clamp screws are not universal. But the screws can be reused in most cases, and the screws in the kit match a large majority of the 109s I have come across.

Mine definitely needs new screws. I have always been a diy person, hoping when I bring them in I can have a good talk with the tech. If that does not pan out. I will put them on the back burner until I obtain more knowledge.

 

[dstalsby5]

I appreciate all the info, opinions and advice. Without people on here taking there time.. People like myself would be at loss.

 

[halocline]

I am keeping the Mk5, in my mind or read that the mk10 was a better first stage. In truth I care more about being in the water then I do what I am using. I tend to put the cart before the horse at times.

Keep in mind that you have a MK10+ according to your post and that is a very different animal than a MK10 IMO. Same exterior but all the working parts are different, and most of us that are fans of these prefer the regular MK10.

 

[Eric Sedletzky]

Keep in mind that you have a MK10+ according to your post and that is a very different animal than a MK10 IMO. Same exterior but all the working parts are different, and most of us that are fans of these prefer the regular MK10.

How can you tell the difference between a regular MK10 and a MK10plus?
In case I ever run into one.

 

[halocline]

MK10+ has a satin seat retainer, regular MK10 has chrome. I assume the ones that were sold new as pluses had plus on the yoke knob

 

[Angelo Farina]

I am keeping the Mk5, in my mind or read that the mk10 was a better first stage. In truth I care more about being in the water then I do what I am using. I tend to put the cart before the horse at times.

Yes, your latest-model MK5 is better than the MK10 Plus you have got. If it was a standard MK10 with knife-edge piston, then it would be on pair with your MK5 last model.
Also note that the MK10 "non plus" and the MK5 share the very same service kit, which is still available on the Internet.
The only benefit of the MK10 "non plus" over the MK5 is that the current inexpensive "universal" Scubapro DIN conversion kit works "plug and play" on it, whilst for installing it on the MK5 you need some mechanical adaptation, and this goes out of Scubapro recommendations.
You should find the original MK5 DIN adapter, but this is difficult to find and possibly more expensive. I managed to get only one, for one of my 6 MK5...
On other two of them I installed the modern Universal DIN kit but, as said, this required some adaptation.
I warmly suggest that you convert all your regs to DIN, of course!