Is it possible that you live at over 12,000 feet some where in Texas? This could easily account for the overly low reading.
What am I doing wrong? Compression testing
- Thread starter rxpx40
- Start date
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How much does it drop per thousand do you know?
Rockjock
Addicted to ArboristSite
It is not the same valve that you use in your car tire. If you compare them they look the same, be it 1 is red the other white but when you press the valve you will find the white 1 has very little resistance.. swap them out and have a look to see how the reading changes. In my Mac unit it was about 30 PSI difference.
Big_Wood
westcoast dweller
so what your saying it is the same valve LOL just a different spring within the valve.
Rockjock
Addicted to ArboristSite
YES kinda sorta. They are both Schraeder valves but for different uses. The MS 171 and MS 661 are both chainsaws but very different.
Dammed Canadians
Mine leaked when I put the adapters on it and it showed lower compression than when I took the adapter off.
cedarshark
Addicted to ArboristSite
Sounds like bad "o" rings on the adaptor
LegDeLimber
Addicted to ArboristSite
LegDeLimber
Addicted to ArboristSite
Those cores will be fine for nearly any testing.
Just take note of the remarks about having the stem at the end of your gauge
so as to not add extra volume that will give a lowered reading.
Just take note of the remarks about having the stem at the end of your gauge
so as to not add extra volume that will give a lowered reading.
MarkEagleUSA
ArboristSite Guru
My Craftsman tester has a 10mm adapter.
cedarshark
Addicted to ArboristSite
This is interesting. So, if you have a saw that has 150psi compression at sea level it will only have 77% of that compression (115 psi) if you are above 8500 ft altitude ? Am I getting this right ? If so, this altitude adjustment is a major deal for you high country dwellers.
May have been but it was brand new. I chose just to not try the adapter unless really necessary. Most chainsaws that I've seen don't need the adapter anyway to check compression.
cedarshark
Addicted to ArboristSite
If you don't use the adaptor to match the spark plug threads.....how do you screw the gauge into the plug hole ?
The threads on mine are both the same. The "adapter" on mine is merely an extension to get at hard to reach places. I guess I misused the term "adapter". Actually, all the chainsaw plugs anymore, as far as I know, use the same size threads.
Rockjock
Addicted to ArboristSite
CS I am not sure what brand of tester Jr has but all of mine 1 MAC and 2 cheapies can be used without the adaptor on the chainsaws I have worked on.
HuskStihl
Chairin'em for the sound
You just pull till it stops rising
My compression tester works just fine although it's not an expensive one. I bought it new and it may not be the most accurate but it lets me know if my saws need rings. I have a saw right now that has a piston that looks nearly perfect through the exhaust port but only has 90 psi. compression and won't start. I have rings ordered for it but it may require more than that.
