Is my Saws Compression low?

[rolloman]

What would be a good compression # for a Husky 359 that cylinder has been lowered .030" to get squish number to .020". I have finished my saw and it runs and cuts very good but the compression has me kinda worried that I could get some more out of it. It is 90 lbs. I checked other saws both used and new and they all are around 90. I've seen in other threads where this would be considered extremely low. I'm confused since I can't find another saw both old or new that is over 90#. Is this good or should I start questioning my compression guage?

 

[bigbadbob]

Your tester does have the schrader valve in the tip???
Or like you said you gauge is FUBAR.

 

[rolloman]

Yes, it has a schrader valve.

 

[timberwolf]

A cylinder lowered 0.30 should be up about 180 plus.

It had .050 squish stock? A saw running 90 psi will not run "very good", in might run but is likely to be way down in power.

An accurate 90 psi reading is bad, pull em down and see whats up. If not, time for a new gauge, that might be less hastle as 90 psi reading on a good running saw does not add up...

If the gauge needle leaks down after pulling then in might be a bad schrader valve, have had them get loose before too.

 

[rolloman]

Yes it started out stock with .050" squish. I will check the guage tomorow. It seems like it would be hard to pull the rope decompression or not with 180 psi.

 

[troutfisher]

An easy way to check the calibration of your compression guage is to plug it into the air hose. If the guage on the air tank says 140 the compression guage should say 140. (or whatever psi is in the tank)

 

[SawGarage]

check the valves in your gauge, and the function on the compressor, as TF said..

if you can hang the saw by the rope, it has WAY more than 125psi...

J

 

[rolloman]

Checked the gauge today against the guage on the air compressor and it was the same. What I found at is that depending on the schrader valve the readings vary considerably. I used 3 different schrader valves and got 3 different readings of 30, 60, and 90 psi. Until I figure the schrader valve thing out, I'm sure that the my saw is o.k. since it reads within 5 psi. of all the saws in the shop, including the new ones although the all read around 90 psi. I will work on the schrader valve issue so that I can trust the guage which is brand new. Is the schrader valves anything special or are they the same. It seems awfully odd that it is so dependent of this. We checked the hose for a blockage etc. and it all looked good. Anything else you can think to check? If not I will keep checking things and hope I find out what it is and can post the results soon.

 

[troutfisher]

There are plenty of saw shops that would buy that guage from you, that's a saw selling tool!

 

[rolloman]

There are plenty of saw shops that would buy that guage from you, that's a saw selling tool!

Yeah, maybe I can sell it and buy me one that actually works.

Evidentlyy all schraders are not created equally!

 

[bigbadbob]

There is a thread somewhere on AS about the scrader valve.
It just may be special.

 

[rolloman]

Thanks bigbadbob, I went to Chainsaws forum and found tons of threads about compression guages. What I found is that the schrader valve is special for compression guages used for small engines. They have a lighter spring than the guages used for auto engines (something about the smaller volume of air in a stroke from as small engine to open the schrader valve). The ones in tire tubes can have a stiffer spring because the air chuck or an air pressure guage have the part on them that pushes on the schrader valve to open it.

(The following info is what I found in the threads.)

SNAP ON has them and they know the difference between the small engine type.

The Schrader valve is probably worn and is available at NAPA
it is by Balkamp #BK-7009556. Color is white.

The color seems to be white. (the one in mine is black)

Talk at ya later, Im on my way to NAPA.

 

[SawGarage]

Thanks bigbadbob, I went to Chainsaws forum and found tons of threads about compression guages. What I found is that the schrader valve is special for compression guages used for small engines. They have a lighter spring than the guages used for auto engines (something about the smaller volume of air in a stroke from as small engine to open the schrader valve). The ones in tire tubes can have a stiffer spring because the air chuck or an air pressure guage have the part on them that pushes on the schrader valve to open it.

(The following info is what I found in the threads.)

SNAP ON has them and they know the difference between the small engine type.

The Schrader valve is probably worn and is available at NAPA
it is by Balkamp #BK-7009556. Color is white.

The color seems to be white. (the one in mine is black)

Talk at ya later, Im on my way to NAPA.

CORRECTAMUNDO! I was telling you this, when my computer crashed last night...

the springs in the tire schraeder valves is MUCH MUCH stiffer...ask my how I know...

the orig valves in my tester were orange...

the new snap-on's were white..

J

 

[rolloman]

Now I've got 150psi compression.

Got a valve core (schrader valve) with the white band on it from my local CarQest store and all is well with 150 psi of compression now. They looked at me like I was crazy when I asked for a white one, but they were able to find it in their catalogs and ordered it for me. They also didn't know that these valves differed in spring pressure.