Some interesting compression results

Hey guys,

Like the subject says I've got some weird C-test results on my '81 650 maxim (stock intake). The dry results were a little low but all about the same:

1- 100psi
2- 100psi
3- 110psi
4- 110psi

But the wet test is where it gets interesting:

1- 125
2- 150
3- 250 (?)
4- 175

As I understand it my piston rings are probably bad, but is such a high reading normal (#3)? I tested it three time and got around the same readings, the first time it went over 300psi.

The next question is, is engine worth rebuilding? It has about 33k on it and isn't in great shape anyway, should I be looking for another engine? My guess is yes.

Anyways thanks for looking, any advice is greatly appreciated.

 

Is it possible that you poured too much oil in the #3 cylinder causing the compression ratio to shoot up?

 

I would "get a second opinion." (Use a different gauge.) They could be 140-140-150-150 on a different gauge. Actual readings not as important as differential.

I agree you probably dumped too much oil in.

 

I certainly wasn't being very exact with the oil, would that account for the differences in the "wet" test results? I'll see if I can get my hands on another gauge and go from there.

Thanks for the quick responses.

 

The idea of the wet test is to just get enough oil in to seal leaking rings. Adding oil after that just artificially raises the compression numbers. Put enough in and it'll lock the engine, potentially causing damage.

A teaspoon or two is all you should need.

 

I think the best thing to do would be to get it running again and get all the oil burn't off. Run it for a few days and try it again. Remember to use the same amount of oil in each cylinder so your numbers are good.

MN

 

That was gonna be my next question MN, I'll do that and re-test it and let you all know the results. Thanks again.