SP MK20 TIS piston O'ring seals fitting

[bulle377]

Hello,

I have a MK20 TIS and I have on the piston 2 seals :
* 1 PTFE seal
* 1 O'ring.

My question is to now wich side you fit the PTFE and the O'ring ? :
- Is it PTFE side of the tube (that fits on the seat) and O'ring side of Piston end
- Or O'ring on the side of the tube and PTFE ring on the side of piston end ?

Thanks in advance for your reply.

Arnaud

 

[redacted]

Plastic ring closest to the ambient chamber (stem) and o-ring closest to the turret (piston head).

 

[DA Aquamaster]

Yes. they should fit in the same groove with the o-ring closest to the piston head and the split white plastic backing ring closest to the stem.

That is of course assuming you have a Mk 20 piston that uses that arrangement - an all metal piston with a wide groove. If your Mk 20 has the newer composite piston it will have a narrow groove in the piston head to accommodate 1 o-ring and another groove at the base of the piston head to accommodate another 0-ring between the piston and TIS bushing. In that case none of the split plastic backing rings are used.