compression

[jwsimmons]

Does anyone know what a normal compression reading would be for a a973 4hp johnson. I tried and got 45 psi. I thought maybe this is a little low but I'm probably or at least hoping I'm wrong. Thank you

 

[mikeyzx2]

Re: compression

squirt a little oil in through spark plug and try again. if there's a big change then the rings are worn and need replaced

 

[jwsimmons]

Re: compression

I used the oil but no change. For some reason after a few tries the flywheel would get stuck and I couldn't crank it over. I had the engine out for a test run 2 weekends ago and it ran great. I figured it have better compression than this.

 

[OBJ]

Re: compression

Might be a stuck ring jw. Did you do a decarb? Course it could also be a nasty scratch on the cylinder wall. 45psi is low. Might consider just pulling the head and get an eyeball on the cylinder wall.

 

[JB]

Re: compression

Differences in guages and technique can cause wide variations in psi readings, JW.<br /><br />Do you get the same reading (+/- 15%) on both cylinders? Does the engine start and run well?<br /><br />If yes and yes, don't worry about it.<br /><br />If no on either, do a decarb and try again.<br /><br />Good luck.

 

[jwsimmons]

Re: compression

Yes, they are both right around 45 and the engine does run real good. I was just wanting to make sure it's not gonna crash on somone after I sell it. I think maybe I will leave it. The motor and everthing but the cowl looks brand new. The scratches on that are just from transportation. <br /> Thanks guys, I appreciate it.