1 cylinder with low compression

[jgbutler1956]

I've been working on my 1988 Johnson 140 hp trying to get it ready. Checked compression and have 90,90,72,90 on cylinders. Top right low one.
Took off head covers, cleaned carbon off pistons, put "ring free" in fuel new gaskets, and run engine, etc... when I checked cylinders, they looked good.. no scaring, clean, no grooves, pistons didn't have alot of play.. did all the above and only gained about 10lbs on low cylinder.. (went from 60 to 72) Any ideas? Can I run it like this? Are the rings stuck on this cylinder? I haven't cleaned the carbs....will that help? new to this. Thanks for any help

 

[iwombat]

Re: 1 cylinder with low compression

You've probably just got a stuck ring. Go to the FAQ and read up on the decarb procedures. Give it a thorough decarbing and take another reading.

 

[wilde1j]

Re: 1 cylinder with low compression

Try the decarb as suggested. If no improvement, pull and head and inspect. Could be a leaking head gasket, etc. Follow the shop manual for reinstall of head and retorquing, etc.

Use Deep Creep, or Sea Foam (both available at most NAPA stores and others), or BRP Engine Tuner for the decarb (all seem to be the same stuff, at least they all smell the same.)

 

[HighTrim]

Re: 1 cylinder with low compression

courtesy of TD:

i think i would invest in a can of seafoam, in a portable tank, mix 3/4 gallons of premix gas, an 3/4 can of seafoam, (assuming you don't have the vro connected). Put the remaining seafoam in a spray bottle, run the motor up to temperture, remove the plugs, one at a time, spray some seafoam into each cylinder and replace plug. let sit 15 minutes, remove the air silencer from the carb while waiting, restart motor, and spray seafoam into each carb, until it start to stall. repeat till seafoam is gone. run out the rest of the gas. it is going to smoke like it is on fire, and drip goo on the ground. replace the plugs with new ones, and then do the compression check again. this procedure burns the carbon out of the motor and been known to free up rings, and increase compression. let me know the results.