FX Is polishing required? - New Brass FX impact regulator plunger

[bobrel]

First time with a leak in my Impact MKII PP 720 so decided to replace the piston while it was apart rather than polish the old delrin one. Got one from cape fear and was expecting the part to be plug and play but doesnt appear to be.

I test fit it. once the face clears the oring it seems to drag (metal on metal) in the reg body. the plastic one is smooth on the barrel at the edge/face. this one is not..
plastic is 4.0mm at the tip brass is 4.02. measured with origincal digital caliper
The issue is noticeable on pictures. small dings on the edge

Not thinking its good to put it in without doing some sanding polishing but concerned about messing up overall diameter or damaging the delrin piece if i try to cleanup the face.

Also, not 100% sure what the sealing surfaces are and if the dings are important.. the barrel will seal on the oring in the reg body and the face will never touch it once installed.

Suggestions and experiences are appreciated.
thanks
Bob

 

[bchannell]

As long as the body is smooth near the end where it seals on the oring, it's fine. I'm not sure what you're saying about metal to metal contact, but I'm guessing it's oring resistance? maybe? Did you lube the orings inside?
You could ever so slightly chamfer the piston, but I wouldn't go much on that.

 

[MEC17670]

First time with a leak in my Impact MKII PP 720 so decided to replace the piston while it was apart rather than polish the old delrin one. Got one from cape fear and was expecting the part to be plug and play but doesnt appear to be.

I test fit it. once the face clears the oring it seems to drag (metal on metal) in the reg body. the plastic one is smooth on the barrel at the edge/face. this one is not..
plastic is 4.0mm at the tip brass is 4.02. measured with origincal digital caliper
The issue is noticeable on pictures. small dings on the edge

Not thinking its good to put it in without doing some sanding polishing but concerned about messing up overall diameter or damaging the delrin piece if i try to cleanup the face.

Also, not 100% sure what the sealing surfaces are and if the dings are important.. the barrel will seal on the oring in the reg body and the face will never touch it once installed.

Suggestions and experiences are appreciated.
thanks
Bob

View attachment 558677

 

[MEC17670]

I even polish the washers where metal to metal make contact.

 

[Motorhead]

That part ... FYI is called the regulator "SPOOL"
* As too polishing it ... Naw, as its travel when operating is quite small & likely less than .010" Back-N-Forth each refresh cycle

 

[bobrel]

After the first reply I took a reset as the SPOOL (thanks Scott) probably cant touch the inner side of the reg body so any friction must be between the oring and the SPOOL. I lubed the old oring and tried again. didnt feel that great to me but I I'm going with Motorheads recommendation.

BTW that regulator you installed for me is working just fine

Thankyou

 

[bigHUN]

If you decide to put back the original "spool"....
My MK2 from 2020 with over 20K shots in it, I did not replace the Reg all parts still the original, but polish the front face on both parts to mirror finish, only to smoothen the indent.
No leak and no Reg creep.
I don't buy new again and again, I like to fix these things