Compression question

[jommer]

I have a '89 Johnson GT 200 Looper. Top port cylinder was down to 55 psi, the others are 90. I found a burnt ring and slightly scuffed spot on the cylinder wall. I replaced the rings and honed the cylinder. Head looks good. It's now at 60. I have run it, hoping it would come back up. Still 60. Idles terribly.

Would a bad check valve cause it to still be down 30psi on that cylinder?

thanks,
Jim

 

[Bifflefan]

Re: Compression question

First 90 is one the low end of the scale anyway.
As for the 60, your just dragging a dead hole there. 1/4 of your motor is not running and the other 3/4 is not that good either.

Did you just replace the one ring or one set on the one piston?

It may be time to look into an overhaul of the whole thing, or find a good doner.

If that is 6 cylinder then change the numbers accordingly.

 

[jommer]

Re: Compression question

90 is fine on loopers. 95 is about the best you can get. One dead cylinder would be 1/6, not 1/4. Overhaul won't do any good if the there's nothing wrong with the cylinder, piston, rings and head. I was just asking if a bad check valve would cause it to loose compression.

 

[Bifflefan]

Re: Compression question

Wrong motor, i didnt read as good as i should have i guess

 

[kenmyfam]

Re: Compression question

Compression numbers are also subject to the tester being used. They can vary wildly !!! What it does show though is that you have a bad cylinder.
Bad check valve on what ???
Done a thorough decarb yet ????