Nissan compression test

[rythmman]

What is a good value for compression of Nissan 5hp 4-stroke.

I am only getting 50psi dry .... is this OK?

Thanks

 

[jjacobs007]

Re: Nissan compression test

no more than 10% difference in cylinders

 

[pvanv]

Re: Nissan compression test

Of course, as a 1-cylinder, there won't be any variation between cylinders.

50 sounds low. To get a fair test, you need to start with a warmed-up motor, unclip the stop lanyard, attach the gauge, open the throttle all the way, and pull very fast, several times. I would expect it to be over 100 psi.

 

[capnfred]

Re: Nissan compression test

As a coincidence today I was testing the compression on a 5hp 4 stroke I am working on....dry after about 5 pulls with the throttle wide open I got almost 150 psi.....the ignition is my problem....but I am fixing that tomorrow.....as a rule of thumb anything below 100 psi on a gasoline engine is not good enough.... even my old vw bus had over 100 psi..... check the valve clearance..... I am not sure what the spec is... but on a small 4 stroke engine I usually use something around .005-.010 as a ballpark.... has worked well for most small engines I have worked on .... including a chinese scooter which ran over 10k rpms....... I was amazed that little mill could spin that fast.... anyway good luck...

capn