Topic: can i do a compression test with no oil in engine and oil pan off? 81 cb650

[basketcase81]

that is all

[CB650CPastor]

Other guys may have different opinions on this but I wouldn't spin an engine without oil in it.

[Bodi]

Not a problem for a compression test.

[strynboen]

a komp test is not giving a lot of info..if your engine ..not is be running dayly or atleast for 2 or  more auers..before a test...a dry aut and oil free engine vill give a strange low resultat. valvets vill not seat real good..

..so if it is a barn find..or a non runner...get it running and give it a shake Down before try/vaste any time on that
just running a old dry engine vill give better resultats..so get it running and do the test..and see if all cylenders give the same resultat..

[70CB750]

Yes you can. I done it for my 750.

[basketcase81]

Other guys may have different opinions on this but I wouldn't spin an engine without oil in it.

I figured it would be ok, but i didnt like the idea. Im losing my patience with this thing so I did it anyway. 

Not a problem for a compression test.

I got 80 on #1, 90 on #2, and ~110 on #3&4

This bike was sitting for an unknown amount of time and I am in the process of rebuilding. PO didnt put the cam tensioner in correctly and bent all the valves. I got a good used head and these are the numbers i got. Should I keep going or should I look for something else causing those low numbers?

Thanks

a komp test is not giving a lot of info..if your engine ..not is be running dayly or atleast for 2 or  more auers..before a test...a dry aut and oil free engine vill give a strange low resultat. valvets vill not seat real good..

..so if it is a barn find..or a non runner...get it running and give it a shake Down before try/vaste any time on that
just running a old dry engine vill give better resultats..so get it running and do the test..and see if all cylenders give the same resultat..

 

Yes you can. I done it for my 750.

I did. see my reply to Pastor if you can help with that. Thanks

[Flyin900]

Did you test the valves in the used head with a liquid leak test for sealing before installing the head?
Like Strynboen said an engine that has sat for a long time the rings aren't going to seal well and the valves may be suspect in your new head if you didn't test or lap first.
I would get it running as suggested and see where your at after a hundred miles of riding. Soaking the cylinders with ATF and acetone mixture will help free stuck rings and clean out carbon.

[basketcase81]

Did you test the valves in the used head with a liquid leak test for sealing before installing the head?
Like Strynboen said an engine that has sat for a long time the rings aren't going to seal well and the valves may be suspect in your new head if you didn't test or lap first.
I would get it running as suggested and see where your at after a hundred miles of riding. Soaking the cylinders with ATF and acetone mixture will help free stuck rings and clean out carbon.

i did not test the head. I have since got this thing running for a couple seconds with starter fluid (couldnt hook up the gas tank). Now trying to run fuel lines but vacuum pump is missing from carbs

[Bankerdanny]

You put the oil pan on an added oil before you ram or I hope.

[Airborne 82nd]

You put the oil pan on an added oil before you ram or I hope.

oil pan oil gas who needs all that extra stuff Throw a little sand in there well it might already be there. jk

[Gene]

Im losing my patients with this thing so I did it anyway. 

You will need patience with an old bike.  Not trying to be a d&*k, but that's one tool you will absolutely need.

[basketcase81]

You put the oil pan on an added oil before you ram or I hope.

of course

Im losing my patience with this thing so I did it anyway. 

You will need patience with an old bike.  Not trying to be a d&*k, but that's one tool you will absolutely need.

yep, slowed myself down. feeling better now