SP M20/g500-MK25/s600 Upgrade

[will_tekkie]

Hi dear friends...i have a mk20/g500 reg. so i´m thinking to do a upgrade to a new version mk25/s600...

I know this can be done using a upgrade kit, a new composite piston and a couple of o´rings for the IP adjustment screw system...the conversion of the g500 to s600 i´m not sure about parts which will be needed (more than poppet lever?????? and some orings..)

If some of you had done this work i´ll be interested about details (cost..convenience to change all components to reach a mk25/s600 config) and feedback comments...
thanks...Will.

 

[DA Aquamaster]

The MK 25 uses a different seat retainer design that makes the intermediate pressure externally adjustable. A full conversion of a MK 20 to MK 25 status is not worth doing however as the IP adjustment just makes life easier for the tech, not the user (unless they work on their own regs). The MK25 conversion also deals with just the seat retainer and does not actually include the new composite piston. Dealer cost on the conversion kit is around $16.00.

What you do want to consider is going with an AF upgrade which should include the composite piston (PN 10.600.155), the latest ridged version of the piston Thermal Isulating Bushing (PN 10.600.135), the new dark colored soft sleave (PN 10.700.401) and the new finned antifreeze swivel cap (PN 10.600.102) although this doubles the cost of the conversion and is something that you might consider optional. Dealer cost for the piston and other small parts is around $22.00 and the new swivel cap will double that cost.

If you don't go with the new cap on your MK 20, I would at least remove the plastic trim cap that fits over the swivel or remove the rubber swivel trim ring if your Mk 20 is equipped with that instead.

An individual MK 20 could have one of three pistons in it and may already have the composite piston as the only piston used or available as a replacement part since 2-2000 has been the composite piston. If this is the case, the AF treatment is pretty cheap.

A labor charge of $25 per stage is reasoanable and SP does not set any retail price for parts, so dealers are free to charge what they want. They do deserve some profit and and there are also shipping costs over and above their dealer costs, but a 100% markup, while not uncommon, is perhaps a bit excessive as they are also making money on the labor charge. Anyway, you probably have some room to negotiate if you are a good customer.

 

[DA Aquamaster]

Your G500 may or may not be economical to upgrade. SP moved production of the G500 mid stream and the later production units were made to meet European standards with a different case (PN 11.600.006) as well as several other parts which are also used in the S600. So if you have the early American made G500 you will need a new case, exhaust cover, and knob in additon to the lever and some balance chamber parts and of course the S600 purge cover and diaphragm.

All this means the cost of conversion is not really practical for a US version of the G500. The good news is that the US version of the G500 was an exceptional second stage and a much better breathing unit than it's European counterpart. So if you have the US made version, you really don't need the S600 conversion. If I remember correctly the purge cover was black on the US version and grey on the Euro version.

 

[redacted]

While many different upgrades are available, one kit I got for may G500 included a new diaphram and a new poppet. I just kept the diaphram as a spare. But older G500s had either a 2 piece poppet or a one pieces poppet, both with a single o-ring sealing the balance chamber. Of the few problems I have had with the SP balanced poppet 2nd, most have involved the o-ring sealing the poppet in the balance chamber. The newer poppet (probably since 2000 or so) have 2 o-rings sealing the chamber. I believe the second o-ring primarily serves to protect the inner ring from damage. I suggest you get this upgrade if you have a problem (slow, small leak) or when you go for a periodic service. I would not expect it to cost much as the G250 kit includes this complete poppet assembly as so many of them only have the single o-ring.

 

[DA Aquamaster]

The G250 and older G500's used the older 2 piece poppet with a reuseable metal stem with a single o-ring. But the current G250 annual service kits include the new S-wing poppet (with 2 o-rings) and the slightly longer balance chamber that is required with this new poppet, so the old poppet should cease to be a concern at the next annual service.