Saw Compression

[wodbutchr]

Hi you all,

I am a newbie around this forum and have a question to submit about chainsaw compression values. I looked around a bit but did not find the answer and I think there is a lot of experience around here.

What would be typical compression values in PSI for a new saw?
Does it vary a lot between manufacturers and models?

What would be the value when the saw becomes so so, when throwing that saw around and madly pulling the rope as to almost brake it won't start it?

At what value should the rings be replaced if the jug is not scored yet?

And when should the jug be replaced?

So next time I see "a nice used saw" a compression test should tell me the life left in the beast!

Thanks
Andre

 

[Lawn Masters]

For any saw, a simple field test for compression, is to pick it up by the starter handle, if it falls slowly, or not at all, its fine, if it drops rapidly, it needs a piston, rings, or both.

For NEW, I'd say around 160 or so for a 60+ cc pro saw is great, used, they'll show around 120 or so, give or take some. most saws will run on about 90psi, but not very well.

 

[cbfarmall]

So next time I see "a nice used saw" a compression test should tell me the life left in the beast!

Compression isn't necessarily the end-all, be-all indicator of saw life. Pulled apart a Remington reed valve engine once with good compression. The piston was all tore up (from a leaky oil tank). Good compression, but was pretty much toasted. Or a Stihl 042 I picked up recently for parts. Had good compression, but it was poorly modified and the piston was pretty chewed around the perimeter of the top. When oil or gas fills up a cylinder, you'll get really good compression. Though, you ought to be able to spot that problem when it comes pouring out of the muffler.

Just something to chew on.

Chris B.

 

[wodbutchr]

Thanks for the info. The saw was falling pretty fast, so I pulled the jug out.
No scoring, so I presume the rings are worn out.

New rings or new piston/rings?

The local Stilh dealer wants $45 just for 2 rings, which sounds like a rip-off to me. Here in Calgary (Canada) there is no competition, so you high prices with an attitude.

Anybody with a 42mmX1.5mm set of new rings (Stihl 024) they would part with, or any decent supplier (even OEM) who would carry rings/piston?

Thanks

 

[TimberPig]

http://www.stihl.ca/dealerLocator.asp

Try this, it shows 6 dealers in Calgary if you're having problems with the one you're dealing with.

$45 C for a pair of rings doesn't really sound that out of line to me. They are fairly pricey to produce, and OEM parts are always more expensive.

 

[Lakeside53]

Thanks for the info. The saw was falling pretty fast, so I pulled the jug out.
No scoring, so I presume the rings are worn out.

New rings or new piston/rings?

The local Stilh dealer wants $45 just for 2 rings, which sounds like a rip-off to me. Here in Calgary (Canada) there is no competition, so you high prices with an attitude.

Anybody with a 42mmX1.5mm set of new rings (Stihl 024) they would part with, or any decent supplier (even OEM) who would carry rings/piston?

Thanks

Stihl rings are pricey. Often by the time you price the rings and pin, you may as well get the entire piston/rings/pin assembly for a few $ more. The 1.5mm rings are a standard item available for a couple of bucks (more or less) each... Do an Internet search on "2-cycle rings". the later 1.2mm type or weird cylinder sizes (like 44.7mm) are much harder to find.

 

[PWB]

List on that size ring at LASER is about 7 bucks, dealer price a little over 3 bucks (last year's catalog). If there isn't a dealer close that can get them for you, just stop in at their office (Edmonton) next time you're there. They will mail order too. Bailey's will probably sell them too, but then you're dealing with the border................