chain saw compression gauge

quietrangr

On the Bailey's chain saw compression gauge FAQs, a couple of guys have written that (as I understand it), a compression gauge won't give accurate readings if it has a hose because the hose increases the amount of "space" you have to fill up with compression. Does anybody here know anything about this?

sharkey

The deal on the small engine compression gauge is about the length of the hose and if a Schrader (tire style) valve is present in the end of the hose where it meets the connector that threads into the cylinder.

If your trying to use an old style automotive gauge on a 30cc cylinder, there is alot of hose to fill. That is not to say you cant do it, but it might take 50 pulls to find the top number. Adding to this problem is if the tip of the hose doesnt have that valve in there, your refilling the hose every rotation of the crank. This old style tester wont work for you unless it has the valve.

Being that Baileys is familiar with these small two cycle engines, I would think that they would be selling a tester that you can use. Why dont you call customer service and ask. Im sure they will look and tell you right over the phone. Otherwise, stay with a name brand like Mac, Snap On, or Craftsman which is made to be used on a small engine.

When you attempt the test, remove the air cleaner and prop the intake open with a stick or a screwdriver so that the cylinder can draw without obstructions for the best reading. Once you hit whatever number your saw will push, the reading wont go any higher no matter how hard or how long you pull it over.

Good numbers on a modern engine are above 150 psi cold with no extra oil added to seal the rings. 120psi and below will run but its time for a set of rings. Below 90psi, the engine wont run. Some of the older Homelite, Macs and Poulans may be around 120 and that is ok for them because they run a much looser squish.

Best wishes,
Bob

quietrangr

Thanks for the info. That's a much clearer explanation than the postings/questions at Bailey's. I ordered the compression gauge a few days ago; thought there was no way to know without trying. I'll report back here after I try it out.

STEVEGODSEYJR

As long as the gauge has a schrader valve it will work on your saw. It just holds the compression in till you release it. Steve

quietrangr

I bought the compression gauge from Bailey's. It has the little release button at the base of the gauge. It takes four to eight pulls to get the top reading. My 361 Stihl with about 2000 hours read at 130. My 2171 Jonsered with something like 5000 hours read about 110. I think the gauge does the job.