Plastic crank seals?

[CamMann]

Anyone ever used plastic crank seals on a saw? Picked up a broken down project saw (mac titan 70), couldn't find parts numbers or compatibility listings for new crank seals. Guy at the local bearing/seal shop measured the old ones and ordered me some new ones of the same size. Got them yesterday, and they're plastic. First time I've ever seen plastic ones. Guys at that shop are great at what they do, and he knew it was for a chainsaw. So, I assume it'll be fine. Thought I'd run it by some of you first though.

Ultimately, they're easy to replace, and the saw is a kind of cheap, Italian, mostly plastic Mcculloch; not vintage american metal & muscle. So, I don't mind experimenting with these seals, unless someone who knows more than me is certain they're a waste of time. Thanks, as always!!

 

[link]

The original crank oil seals on the ms200t is plastic like, not the standard metal rim with rubber inserts.
Id say use them, I bet they work perfectly.

 

[CamMann]

The original crank oil seals on the ms200t is plastic like, not the standard metal rim with rubber inserts.
Id say use them, I bet they work perfectly.

thanks for the input! yah, I think i'll give them a go

 

[Thommo]

Nothing wrong with those seals. They will have metal under the rubber coating

 

[CamMann]

Nothing wrong with those seals. They will have metal under the rubber coating

good to know, thank you!

 

[Vintage Engine Repairs]

Ideally you’ll want viton as they come in contact with fuel.

 

[ballisticdoughnut]

Anyone ever used plastic crank seals on a saw? Picked up a broken down project saw (mac titan 70), couldn't find parts numbers or compatibility listings for new crank seals. Guy at the local bearing/seal shop measured the old ones and ordered me some new ones of the same size. Got them yesterday, and they're plastic. First time I've ever seen plastic ones. Guys at that shop are great at what they do, and he knew it was for a chainsaw. So, I assume it'll be fine. Thought I'd run it by some of you first though.

Ultimately, they're easy to replace, and the saw is a kind of cheap, Italian, mostly plastic Mcculloch; not vintage american metal & muscle. So, I don't mind experimenting with these seals, unless someone who knows more than me is certain they're a waste of time. Thanks, as always!!

They’re rubber coated steel not plastic. See if a magnet will stick. I could be wrong, but I suspect that won’t be the case.

 

[ballisticdoughnut]

The original crank oil seals on the ms200t is plastic like, not the standard metal rim with rubber inserts.
Id say use them, I bet they work perfectly.

They’re made of PTFE, commonly known as Teflon. The sealing material is anyway. The rest of it is some kind of phenolic material like Bakelite.

 

[lone wolf]

The original crank oil seals on the ms200t is plastic like, not the standard metal rim with rubber inserts.
Id say use them, I bet they work perfectly.

Oh you know about that on the 200t huh. You rebuild one of those saws?

 

[grizz55chev]

Oh you know about that on the 200t huh. You rebuild one of those saws?

I believe theyre bakalite, and easy to break during installation.

 

[lone wolf]

I believe theyre bakalite, and easy to break during installation.

Thats why some people prefer rubber seals they dont break so easy. I prefer the OEM seals they dont break if you are careful.

 

[poleframer]

@lone wolf- I've rebuilt my ms200t and 200 (rear handle-prolly my most used saw, love it) a few times, and thought about seals, and prefer the "plastic" OEM ones.
My reasoning is that the metal ones with rubber and a small spring that holds the sealing flange is similar to oil seals in engines. As such they are designed to keep oil under crankcase pressure IN.
With 2 stroke engines vacuum is somewhat more important than pressure in the crankcase, a vacuum leak causes lean fuel conditions rapidly.
I think there is a youtube repair guy (matt olson) that explains this, and thats why often the rubber seals should be installed "backwards" because the "pressure" side is actually to the outside (meaning he pressure on the seal acts as a billows and forces the seal lip tighter), and I think thats why the OEM seals are shaped as they are in the ms200s. And are supposed to be installed backwards to most engine guys thinking.
Your thoughts?
PS, if this has already been hashed over NVM.

 

[lone wolf]

@lone wolf- I've rebuilt my ms200t and 200 (rear handle-prolly my most used saw, love it) a few times, and thought about seals, and prefer the "plastic" OEM ones.
My reasoning is that the metal ones with rubber and a small spring that holds the sealing flange is similar to oil seals in engines. As such they are designed to keep oil under crankcase pressure IN.
With 2 stroke engines vacuum is somewhat more important than pressure in the crankcase, a vacuum leak causes lean fuel conditions rapidly.
I think there is a youtube repair guy (matt olson) that explains this, and thats why often the rubber seals should be installed "backwards" because the "pressure" side is actually to the outside (meaning he pressure on the seal acts as a billows and forces the seal lip tighter), and I think thats why the OEM seals are shaped as they are in the ms200s.
Your thoughts?

The OEM seals are best they allow less friction which = more RPMS for the first thing. Installing seals backwards is counter intuitive to the knowledge of millions. There is no so called problem that he speaks of typically they seal just fine for many years he can put them in backwards if it makes him feel better. Also I always use OEM Stihl parts in my current builds. I learned years ago stock is best.

 

[lone wolf]

@dmb2613