Compression Testing

[ferrariman]

Should I spray a little oil into the cylinder of a two stroke before I compression test it?<br /><br /><br /> Thanks F-man

 

[tashasdaddy]

Re: Compression Testing

if the motor has not been run in a long time yes, tilt motor up and let soak in, the lower engine and turn over with out plugs, to blow excess out. if it has been run resently no.

 

[CFronzek]

Re: Compression Testing

I would do it both ways. It's well known that you'll get higher numbers with oil sealing the piston. But, you'll never be able to get that much oil around the piston in normal operation. <br />A cylinder that shows a big jump in pressure after oiling is a cylinder that has ring problems.<br />The old time procedure was to warm the engine up to get the pistons up to working temperature, kill the spark, kill the gas flow, open the carb all the way, test the cylinder w/o oil, then w/ oil. <br />With oil, the oil overrides the piston rings and you want to know how well the piston rings are functioning.

 

[Scaaty]

Re: Compression Testing

On a 2 cycle, Tash is correct. Chuck. your correct on the both ways, as it might show an increase. But the adding of oil was mostly for 4 strokes, to see if a low PSI cylinder would increase PSI with oil added. If it did, it was rings, if not, bad sealing of valves.<br /> But you both forgot to mention to open the throttle! Gotta have air!