Compression

So...I tested my compression, I had all 4 hanging around 120 ish is this ok? it's hard to crank with the starter as my starter is junk and catches and slips and so on but just looking to see if this engine will run with 120 for compression

1977 KZ1000-A1 per FSM:
Standard Cylinder Compression 128-156 psi;
Service Limit 100 psi with less than 14 psi difference between cylinders.

So 120 psi may be okay, depending on which bike, year and model.

Good Luck!

you dont want to see more than 10% between the cyl compression although it would help to know the bike and the miles

Sorry it's a 78 kz650

with 34 on the clock, pulled it out of a guys garage where it sat for a decade, it runs, but only on choke so I'm tearing the carbs down tomorrow but I'm just wondering if 120 is ok, I don't want to do a rebuild on the motor, just get it running to ride for now and teardown over winter

120 is not stellar, but adequate.

Skyman wrote:

120 is not stellar, but adequate.

Exactly.
It WILL run on 120,and in some cases,it'll run GOOD on 120.

axisfx80 wrote:

So...I tested my compression, I had all 4 hanging around 120 ish is this ok? it's hard to crank with the starter as my starter is junk and catches and slips and so on but just looking to see if this engine will run with 120 for compression

Cold or hot? Cold that's actually pretty decent for an old engine. Hot, not so great but run it until it drops....

Thats cold and with the kick starter, and the throttle open I know it runs, but I have the carbs off and broke down for cleaning, I was just curious if it would be ok till the winter when I can rebuild

axisfx80 wrote:

Thats cold and with the kick starter, and the throttle open I know it runs, but I have the carbs off and broke down for cleaning, I was just curious if it would be ok till the winter when I can rebuild

120 psi cold ain't bad. I'll wager it goes up 20 or 30 when fully hot.