71 johnson 125 piston

[sean125]

Hi i have a 71 johnson 125. I did a compression test on it and #1 was coming up vary low.So i decarbed it all that good stuff to see if i could get it to come up someone said maby its stuck because it was sitting for 3yrs. Well it didn't get any better.So i pulled off the head and saw that the #1 piston is 1/2 way gone.anyone have any advise. can i change just the 1 piston and it be fine? what may have caused it? thanks for any help.

 

[Joe Reeves]

Re: 71 johnson 125 piston

That problem is usually caused by having the full spark advance timing set too high, OR a small stream of water entering the combustion chamber, OR a slightly clogged carburetor that would cause that cylinder to run lean.