What is the compression on a new two cycle string trimmer? What is the lowest compression where it will still run? The compression on mine is 45 psi, trying to determine how much life is left in the old gal
String Trimmer Compression
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What kind of trimmer is it?
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Use 100 psi as a bare minimum here as I have only seen one unit in 12 yrs that even try to run below 100 psi. New compression varies by manufacture and the equipment but 120-150 psi is quite normal. But if the unit squish have been modified can be over 200 psi at times. Now the Stihl 4 mix system has minimum compression of 87 psi but it is actually a 4 cycle trimmer.
Modern 2 cycles may only have short blocks available which can cost well over 50% of a new unit especially the cheaper ones. And this is if you do your own work. Here I just kill off most units that cost under $150 because by the time I charge for a PNC and labor it is already 3/4 of that if not more. An example is my Poulan 4218 chainsaw. It cost new $139 plus tax and the parts alone ran $98.
Modern 2 cycles may only have short blocks available which can cost well over 50% of a new unit especially the cheaper ones. And this is if you do your own work. Here I just kill off most units that cost under $150 because by the time I charge for a PNC and labor it is already 3/4 of that if not more. An example is my Poulan 4218 chainsaw. It cost new $139 plus tax and the parts alone ran $98.
bertsmobile1
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Getting an accurate secondary pressure reading an small 2 strokes can be very problematic
Compression testers with flexiable connections can expand to a volume substantially bigger than the volume of the combustion chamber
Some times it takes 100 pulls till a compression tester stops going up and that is how you have to do it , just keep on pulling with the trigger wired flat chat till that tester stopd moving
Then post the number .
Using a tester according the instructions ( 6-10 pulls ) will never give an accurate reading on anything under 100cc
Compression testers with flexiable connections can expand to a volume substantially bigger than the volume of the combustion chamber
Some times it takes 100 pulls till a compression tester stops going up and that is how you have to do it , just keep on pulling with the trigger wired flat chat till that tester stopd moving
Then post the number .
Using a tester according the instructions ( 6-10 pulls ) will never give an accurate reading on anything under 100cc
olgeezershonda
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If it still works keep using it until it dies.
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Mostly Bull....
It all depends if you are using the right compression tester or not. It is primarily the placement of the schrader valve and it has to be a schrader valve with the correct spring rate. Those from tire valve stems usually have too heavy of spring rate. If it is in the wrong location you will never get a correct reading. Many automobile compression testers has the schrader at the gauge, plus the schrader spring is too high for small engines. The schrader valve must be at the end of the hose at the cylinder end; otherwise, the hose must be filled each time before it can even try to open the schrader valve..
I use an Actron compression gauge and usually get a correct reading within three to five pulls even on the 21 cc engines and it has about a nine inch flexible hose. You never will find me pulling 100x.
My string trimmer is a Toro Model 51934. I also have a two cycle mower of 1980's vintage that also has compression of 45 psi and it runs just fine. Why the difference? I can't rule out the possibility that my gauge is bad, I suppose.