Topic: Fiber carb shaft seals

[brewsky]

Getting ready to make up a set of washers (seals) to replace the deteriorated originals in my PD carbs,

I have found mostly poly material in either soft or stiff versions available locally. (made from re-cycled plastic bottles).... Also some wool.

I assumed the original was some kind of cotton, but who knows?

Anyone?

[harisuluv]

originals are felt, serve as just a dust seal. 

[brewsky]

originals are felt, serve as just a dust seal. 

Yes, but I didn't realize there were so many different types of felt to choose from.

I picked up a couple sheets at the local fabric store that looked ok.

When I got home and read the fine print on the label, they were made of "post consumer recycled plastic bottles" and wondered how that might stand up to modern corn gas?

Now I'm thinking the wool felt would be better, since it is listed for the SAE specs:

http://www.sutherlandfelt.com/felt_apps.htm

What do you use in your re-builds?

[harisuluv]

those seals aren't in contact with gas.  i might make some out of plain felt if they are MISSING but they aren't worth replacing if they are there.  For some reason a lot of people kind of obsess about them but it's a very trivial "part"

[brewsky]

those seals aren't in contact with gas.  i might make some out of plain felt if they are MISSING but they aren't worth replacing if they are there.  For some reason a lot of people kind of obsess about them but it's a very trivial "part"

Well.,,,, mine weren't "missing" till I blew them apart with compressed air !

Took the rack apart and soaked each carb before I remembered about them

Just remembered I have some left over pool table felt somewhere,.... that may fit the bill.

I never understood why some were rubber seals and the others felt?

[RAFster122s]

Their purpose is to protect the shaft to carb body area from grit making it into the shaft to carb body area and wearing the hole oval or larger allowing air in and requiring the body to be sleeved and new shafts if it can be rebuilt. Otherwise, it is junk.

[harisuluv]

general felt will do.  i wouldn't worry about it too much, neither of them is meant to be a real seal.  Keep in mind the vacuum sync procedure involves removing the cap, so it's not meant to or needs to be air tight or even close.

[brewsky]

Ok....not to worry too much, but just curious why some felt and some rubber seals?

On the choke shafts, all are felt except the two outer caps on #1 and 4, (and inner #2), and there are no inner bushings. Any dust that could slip by could dirty the works and enter the cylinder.

On the throttle shaft, #1 and 4 have solid end caps, with felt washers and brass bushings on their insides.....2 and 3 have rubber seals on both sides with no inner bushings? Since there is no vacuum behind these, nothing would enter the cylinder from there.

It just doesn't make sense to me why, on the same shaft, they have 2 different types of "seal" used.