1 low cylinder compression - can it run?

[jgbutler1956]

I have stripped,sanded,painted,re-cushioned,new hardware,painted again, new gauges, drained foot, de-carboned, pulled heads, new gaskets, new plugs, new impeller, etc... I am worn out....now cleaning last 2 carbs...1st 2 carbs were clean... ran ring free in gas and seaform thru the carbs....before cleaning carbs, it ran, but not great.... after I get these carbs clean, can I run this motor if compression stays 90,88,90,72? When I cleaned the carbon off the piston heads, the cylinder walls looked good... no scoring, gouges, etc
No excessive movement ... do I need to go thru setting timing, etc.?

 

[OBJ]

Re: 1 low cylinder compression - can it run?

Hi jg....

The 72psi puts the cylinder well out of the 10 to 15% range between cylinders. Did you use new head gaskets to reinstall the heads and torque the head bolts in the proper sequence and to spec torque?

Although you may have used Ring Free, there is still a chance you may have sticky rings on the piston. You can pull the bypass cover (if the engine has them) over the cylinder in question and inspect the rings....or a part of them any way. With a small screw driver, push on the rings and see if they will compress a little. If they don't, rings are likely stuck.

No scoring in the cylinder is good. But I would take a look and try and find the problem before running and normal use.

 

[R.Johnson]

Re: 1 low cylinder compression - can it run?

I would groom that dead horse some more.

 

[Walker]

Re: 1 low cylinder compression - can it run?

You didn't say what motor you have but it sounds like its just an old tired engine. Personally, if it starts easy and runs good, I'd just run it like it is til it dies.

 

[jgbutler1956]

Re: 1 low cylinder compression - can it run?

Its' a 1988 140 hp Johnson ... I'll try some more ring freeor seafoam in that low cylinder..
Don't see how I can peek at the rings without taking it apart... It cranks and idles, but I can tell it isn't quite right. Wish I was good at checking the timing and setting it .. might try to get my neighbor who knows more about that than I do to help.
Thanks

 

[tashasdaddy]

Re: 1 low cylinder compression - can it run?

you need the manual to do the link n sinc. hope it's your guage and the readings are inaccurate. try another guage. i thought you were talking about a 70's motor.

 

[kenmyfam]

Re: 1 low cylinder compression - can it run?

Its' a 1988 140 hp Johnson ... I'll try some more ring freeor seafoam in that low cylinder..
Don't see how I can peek at the rings without taking it apart... It cranks and idles, but I can tell it isn't quite right. Wish I was good at checking the timing and setting it .. might try to get my neighbor who knows more about that than I do to help.
Thanks

I have a 1985 140hp Johnson. My compression is between 135 and 140 with my tester and 130 to 135 with my neighbours. You may have a wildly inaccurate tester or a compression issue to deal with.
Get a manual !!!!

 

[jgbutler1956]

Re: 1 low cylinder compression - can it run?

I have a manual.... just not equipment (timing light) to set the timing. My understanding is that 90lbs is ok on my model. Anyone else know?

 

[tashasdaddy]

Re: 1 low cylinder compression - can it run?

some parts store loan or rent them.