compression test question...

[Ranger 330V]

I'm sure this is probably normal but since I haven't checkd compression very many times I figured I'd ask you guys. I checked compression on this engine a while back before I got all the bugs worked out of it and before I was able to run it and it sat right around 115 to 120 on all cylinders. The engine was cold but I had 2cycle oil I had squirted in it as the engine had not been run for many years...did this just as a precaution and allowed it to set for about a week and turning it by hand daily. Today after getting it running I checked compression to show my class how to do it and all cylinders this time were all dead on with one another. But compression was now 100psi. Do you think since it has been run and the oil by itself is no longer present would be the reason for the drop?? I've only run a gallon of gas mix through it so far. It is still on a stand. I'll be putting it on this weekend and taking it next week to run. I think I'll check compression with it warm...I know that will make a difference. 100 is good on a cold engine I've read..but the 115 to 120 i like better. Do you guys think after running it a while the numbers will probably change somemore?? I am going to do a good decarb on it next week also. Thanks.

 

[bgbass.1]

Re: compression test question...

once you decarb you should see a difference plus if its warm you get a better reading. But 100 ok I know more is better but after you run it a while and let every thing seat itself should be good. Im glad to hear you got it going good.

 

[crb478]

Re: compression test question...

squirting oil in the cylenders will help raise the compression numbers because the rings will seal better against the thicker straight oil. You were using the same gauge weren't you? Different gauges also vary a good bit. The improtant thing is that all the cylinders are even. As mentioned before a good decard and a warm engine will likely increase you reading also.

 

[Ranger 330V]

Re: compression test question...

Thanks, i'm glad to have it going now. I had had trouble with the trigger and stator...but didn't need to replace powerpacks..but I did anyways. The gallon of gas I run through the motor was mixed heavily with oil and had a can of seafoam in it...but when I get it out I'm going to do a true decarb. Thanks again...the compression gauge was the same by the way.