The correct kind of compression guage

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This topic comes up every week and often more frequently. You absolutely MUST have a Schrader valve at the tip of your compression guage for use on a small 2-stroke engine. If it does not, you cannot use it, period. A Schrader valve is what's found in the stem of your car rims. The reason it is required is because of the small volume of these engines. It is not enough to pump up the pressure of the hose with every pull and you will end up with a way low reading. I wonder how many engines have been torn down that were perfectly fine? Some guages have a release valve up by the guage. That is not sufficient and does not take the place of the valve at the tip.

This is the valve that you MUST have.
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This topic comes up every week and often more frequently. You absolutely MUST have a Schrader valve at the tip of your compression guage for use on a small 2-stroke engine. If it does not, you cannot use it, period. A Schrader valve is what's found in the stem of your car rims. The reason it is required is because of the small volume of these engines. It is not enough to pump up the pressure of the hose with every pull and you will end up with a way low reading. I wonder how many engines have been torn down that were perfectly fine? Some guages have a release valve up by the guage. That is not sufficient and does not take the place of the valve at the tip.

This is the valve that you MUST have.
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This needs to be a sticky in BOLD letters
 
That's the whole idea. We've beat this topic into the ground so many times it isn't funny. It's time to put this thing to rest and help out a bunch of good folk while we're at it.

I'm sure Gary would approve :agree2:
 
I use an uber expensive Mac Tools Gauge. I always wonder if it was worth the 157+ dollars off the tool truck...I wanted to buy an el cheapo schrader valve model from Harbor Freight, but my better judgement called up the local MacMan.
Compression Tester "Bling" courtesy MacTools. Brand: MacTools Part # is CT155
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compression gauge

Hello Brad
I think it is us newbies that are beating this to death.I know myself that before I go and purchase a tool I want to buy the RIGHT ONE.It is hard enough to find dollars sometimes for good tools,but to keep buying the wrong tools is even more expensive!Then there's the never ending,brand debate which for a newbie drives me crazy,you end up second guessing yourself,and don't buy anything.How about if you could post something like this.Taking quality and expense into account,that would end it for me
Thanks Lawrence

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i thought a compression tester without the valve would give you a high reading...at least thats what i have heard...mine has the schrader valve so i wouldnt know.
 
i thought a compression tester without the valve would give you a high reading...at least thats what i have heard...mine has the schrader valve so i wouldnt know.

Mine has all kinds of different connections, valves and other stuff I've never ever used and probably never will. Came in a nice plastic protective case too! I imagine the only tester more accurate than my Mac one might be the Snap-On, that is if they aren't made by the same company!
 
this is the gauge i bought from Autozone. it is an Actron.

someone (Brad) should also cover the proper way to test compression... i.e. throttle position and why it is important. engine temp, etc....

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I usually test my engines cold. It's fine to test hot, but the reading will be 10-15 PSI lower. Yes, lower. Logically I would think it would be higher with thermal expansion, but that's not the case.

It's usually recommended to keep the throttle at WOT for a compression test so that the engine has no trouble drawing fresh air in. However, myself and others have found no difference in the readings. I do put the saw on fast idle when testing.
 
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