Checking saw compression

[muncybob]

Is there a standard number of pulls to reading a saw's compression. One I am looking at I was told is just under 150 lbs at 5 pulls.

 

[smokinj]

Thats a few pulls to get the compression up.

 

[muncybob]

That's what I thought...shouldn't it be 2 or 3 max?

 

[smokinj]

That's what I thought...shouldn't it be 2 or 3 max?

I would be nice to check it on 3 4 and 5 and do an ave... But 150 not bad for an older saw on 5 pulls.

 

[Danno77]

a saw with really crappy compression wouldn't get that high even after 5 pulls. I could have been reading 130 or so around 3 pulls and he just kept checking to see how high it would go.

I usually see sellers posting compression after 3 or so pulls, 5 seems high, but it's not crazy.

 

[HittinSteel]

When testing compression, pull until the gauge stops rising. 150 in 5 pulls sounds healthy to me.

 

[Battenkiller]

When testing compression, pull until the gauge stops rising. 150 in 5 pulls sounds healthy to me.

What about saws like my 357XP that have an auto-compression release valve?

 

[HittinSteel]

Auto? not sure I'm familiar with that........ but on saws with decomp buttons, test without the decomp pushed in

 

[Battenkiller]

Auto? not sure I'm familiar with that........ but on saws with decomp buttons, test without the decomp pushed in

Apparently it wasn't the best idea. If they fail, you can trash your P&C. Husqvarna actually sent out a service bulletin about removing them and putting in a manual decompression button. Mine still has the auto feature.

 

[wendell]

Mine still has the auto feature.

You like living on the edge? Pretty cheap fix to save your saw! ;-)

 

[Beowulf]

When testing compression, pull until the gauge stops rising. 150 in 5 pulls sounds healthy to me.

+1

Agree that the number of pulls should be until it stops rising. Different gauges will have different volumes of space between the MANDATORY schrader valve and the gauge.

Saws have such small displacement that it will take some revs to compress enough air to level out the pressure in a hose volume that could easily be larger than the combustion chamber. (My old Snap-on gauge has quite a length of hose, a quick connect, then various tips for the different types of plug threads.)

You really want to know how much pressure the rings will hold. Number of pulls just adds a variable that is irrelevant between different displacement saws.

You probably want to test it cold, as well.

 

[Danno77]

good info here. I guess I have been doing it wrong. Actually, the numbers I get are probably the same, it just never takes 5 pulls for me. that's the part that I was confused on.