[bigtime400]

Hey I bought a compression tester and I was wonding if you guys could give me any advice for using it on small motors. I have one LB and a MTD with a Briggs 4.5 hp that I want to take a look at. Do you just hook it up and pull the cord? Is that all thats to it? What PSI am I looking for for each? Thanks.

 

[Orangedotfever]

Give it 3 or 4 good full pulls and read the max pressure that was built up.

 

[FergusonTO35]

What he said, plus remove the air filter, turn the choke off, and set the throttle wide open before you test. After you get your first reading, add a teaspoon of motor oil through the spark plug hole, then retest. If compression jumps up significantly you have worn rings.

 

[bigtime400]

Now if I do a test and it shows over 80 psi and I leave it and it shows no leak down it should be ok too right? Because I did this assuming that they must be good. Changed the oil fired it up and mowed my back lawn and it seemed fine. No blue smoke at all.

You would only need to do that if you were indeed loosing pressure and needed to find if it was the rings that were bad or a leaky valve or whatever.

One more thing.... why would you need the throttle wide open and the air filter off?

 

[badfox9389]

One more thing.... why would you need the throttle wide open and the air filter off?

Max air flow

 

[Orangedotfever]

One more thing.... why would you need the throttle wide open and the air filter off?

Don't worry about it. You won't see a noticeable difference.

 

[440roadrunner]

Does cranking the engine work on these small engines with auto compression releases?