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Cityboy
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What I find interesting is that people say if you have less then 90 psi of compression on your 2 stroke engines then there no good and are in need of a rebuild. I have 8 total and none of them have that much compression but all seem to run just fine. They start within one to two pulls and don't seem to bog down in taller grass. Can someone share some insight on this subject for me please.
 

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The Sea of Green Machines
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Depends on the engine. D series engines only have a max of about 70 with an average of about 60. Later engines like the F and E have higher compression. Just go by the published specs for the engine, not some vague generalization.
 

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5K Poster!!!
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I also think the piston ported engines such as the "M" series and the Suzuki two cycle have higher compression ratios...

I wouldn't worry about it if its running good. I have an old Robin trimmer that has low compression but still runs great....I'm gonna use it till she won't start anymore.

I also think that if you get in there and break up some of the carbon deposits in the ring grooves you will have an increase in psi. Use a detergent like seafoam or mmo in the fuel.
 

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It all depends on the different types of engines. 90 PSI should be fine for lawn boy engines, But on some chainsaws or a dirtbike that is low. My Dirtbike right after a fresh complete engine rebuild is about 140, some big CC stihl saws have 175 psi for compression...
 

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Pretty sure the M falls right in line with the others Indy. 115 COLD.

Right....I was diferentiating the piston ported engines from the reed valve engines. My "M" runs 120 cold easy and its never been rebuilt and its 20 y/o!
 

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hmm, yep like snowflakes no 2 alike lol
my new to me snow thrower the specs say 80+with the compr. release deal on it(briggs 3hp 2 stroke motor)
 

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Just wondering..... anyone know what what the compression should be for the Tecumseh tvxl840 2 cycle engines??
 

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i tried to do some diggin,
that motor has a comp.release....if you test bout 80 or better, its in good shape
 

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2 stroke enthusiast
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Just wondering..... anyone know what what the compression should be for the Tecumseh tvxl840 2 cycle engines??
It's strange as even the repair manual doesn't give specs on compression. Mine have tested around 100-105 I think it was.
 

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Thanks for the info :trink39:
 
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