What are the steps of checking compression.

[petermct]

I got a gauge around here somewhere along with all the tubes and end connectors.<br /><br />Anyone want to give me the straight and narrow few steps of checking the compression on each cyclinder?

 

[hondon]

Re: What are the steps of checking compression.

Remove the spark plugs,advance the throttle to wide open[this can be difficult sometimes]. Install the apparatus,and crank away.Five or six pumps on the dial should be enough, and then you have your reading.

 

[petryshyn]

Re: What are the steps of checking compression.

Hi petermct<br />Here is just a few guide lines that come to mind...<br /><br />*start with a fully charged battery<br /><br />1) warm up engine, then shut down<br />2) disable ignition:<br /> >flick lanyard, or<br /> >ground each plug wire to block, or<br /> >unplug power pack, or<br /> >unplug CDI charge stator<br />3) remove all plugs and retain their order for trouble-shooting (appearance)<br />4) throttle wide open<br />5) install gauge and crank engine so the gauge gets 5-7 hits<br />6) repeat the exact same number of hits per each remaining cylinder and record readings<br /><br />*each model will have an OEM parameter for pressure and variation<br />*10% variation from the highest to lowest reading is generically acceptable.<br />*different gauges may give different readings, but they all will reflect variation. Thats what we're most interested in... <br /><br />Hope this helps.....

 

[petryshyn]

Re: What are the steps of checking compression.

Sorry, hondon, I was typin while you were postin....didn't see you till I posted

 

[petermct]

Re: What are the steps of checking compression.

Ok, my gauge also has the pump/vacuum test ability.<br /><br />This looks like a passive test and a vacuum test would check for worn piston rings/leaks when the piston is TDC?

 

[petryshyn]

Re: What are the steps of checking compression.

Applying a vacuum to the combustion chamber is not a valid test. The rings are shaped in a manor which forces them tight against the cylinder when under pressure. Applying a constant pressure and measuring the flow past the rings at TDC would be a feasable test..(leakage test) I doubt you have the equipment to measure that.<br /><br />Good luck!

 

[hondon]

Re: What are the steps of checking compression.

A cylinder leakdown test can be a valuable tool in determining your engines health,but it invovles pressure and not vaccume.Basically you are applying compressed air pressure to the cyl.then with the gauge on the tool,measureing the amount of compression lost to blowby.On a conventional two stroke I would reccomend turning the engine over with the tool installed and charged to check cyl. condition from bottom to top of the bore. You will need a breaker bar on larger motors to accomplsh this task,and be careful,that bar can let loose and crack you in the head if you plug the tool in without removeing it.Got the bridgework to prove it.