What are acceptable compression numbers?

[mcash65]

I am looking at a 1995 Speedster tonite. I asked about compression over the phone and the owner said that he got 115 per side. I have read other posts on this site saying that a new motor will get 140+ but what is acceptable? A post on another site said that anything below 100 will mean a rebuild very soon. What do you guys think?
Thanks, Mike

 

[parrothd]

It depends on the gauge, sometimes they're way off, or not testing right, bring yours and test it.

It should be closer to 140-150, as long as both cylinders are close 5-10lbs you should be fine, but the higher the number the better...

 

[Phildoo]

Way I understand 120 is minimum.

 

[parrothd]

Yea, but when someone says a low number like that but both cylinders are near the same I tend to believe the gauge is bad, doubtful both cylinders are that bad, usually one is 140ish and the other is 20... I always bring mine and test it to be sure...

 

[cli55er]

mine were 135 all around, same model.

 

[Dr Honda]

150 psi is spec for that engine. 135 psi is the bottom of the service limit. (where you can safly go out and play) The engine will still run down to about 125 psi, but it will eat it self in short order, and have limited torque. 115 psi.... that engine is DONE ! It will run on the trailer, but I bet it wouldn't rev up in the water. If you try to run that engine, the blow-by will overheat the lower half, and will destroy the crank bearings, and seals.

 

[cli55er]

you were probably responding to the orignal poster, but i plan a top end rebuild in the next season or two. right now i threw all the money at fixing the pumps.

 

[Dr Honda]

you were probably responding to the orignal poster.....

A little of everyone.

You, at 135... you have at least one more season, but if you do a top-end, your crank will live longer.

 

[MIGUEL CARBAJAL]

Hello guys, I got a few questions, I'm STUMPED!!! with my ski...I got a 96 GTX (787), checked the compression last summer got 145/145 PSI on the cylinders so i was pretty happy. I ONLY used the ski 30 min after i did the compression test, then i put it away for the winter. So this past weekend I stared it. Noticed alot of white smoke and oil comming out the exhaust (which i kno is kinda normal after sitting for a while). Ran the ski (a few mintues at a time) on the water hose for a total of about 10-15 min (thinkn oil would burn away) but the smoke and oil continued. Oil coming out the exhaust worried me so I checked the compression yesturday and got 90/90 PSI on the cylinders!!!

WHAT HAPPENED!!!....how does that happen?...didnt belive it so i used to differnet compression testers and got the same: 90 PSI both cylinders. ski appears to run fine on trailer with water hose, turns on fine. How could both cylinders go bad and have tha same PSI?

Any ideas anyone????

 

[MIGUEL CARBAJAL]

Also the battery was FULLY charged, I did the WOT while testing compression, and I used two differnet compression testers and the testers held the PSI so I dont think they were leaking or workn improperly.