Zero compression....

[woodlandsrider]

Hey guys!

New here to the forum. I have a 1980 CB750k and just rebuilt the seized engine it had. I installed new rings, gaskets, and put it back together exactly as the manual states it should. One big problem...all cylinders have zero compression. Now I thought it was the pistons and rings, although I don't think every single piston would have zero compression. I am thinking it has something to do with the cams or valves...


Any thoughts?

 

[dirtdigger]

Sounds like tight valves or cam timing is way off. Did you mess with any of the shims? Both cams synched correct? Only thing I can say is get it on TDC and double check all the cam timing marks and check valve lash.

 

[woodlandsrider]

Awesome! Ya, I was thinking the timing or cams. Do you know of anywhere that has the info on how to check all of this? D

 

[Travis]

The service manual should cover it. You should be able to download it or I'll could send you the relevant sections.

 

[woodlandsrider]

The service manual should cover it. You should be able to download it or I'll could send you the relevant sections.

Awesome! Would you mind sending me that??

 

[MK3Brent]

Confirm your gauge is working correctly.

You should be getting something.

Does it move at all?

 

[dirtdigger]

Your first post says you assembled by the manual now you want to know where to download a manual? Just trying to sort out the information here. First things first, you need to recheck the timing on the cams and check clearances. Do you have a manual??

 

[woodlandsrider]

Sorry about the confusion! I have a manual, but nowhere in it does it show how to adjust valve timing

 

[dirtdigger]

How do you know the cams are timed correctly when you put the motor back together?? Its not an adjustment...the cams are timed when you are installing them into the head with the chains. What procedure did you use to install the camshafts and cam chain? I would PM Travis and have him send you the motor section of the manual and then go back an verify you installed the cams correct.

 

[woodlandsrider]

How do you know the cams are timed correctly when you put the motor back together?? Its not an adjustment...the cams are timed when you are installing them into the head with the chains. What procedure did you use to install the camshafts and cam chain? I would PM Travis and have him send you the motor section of the manual and then go back an verify you installed the cams correct.

I installed them to the procedure they instructed in the manual but it puts out nothing...

I tested the gauge and it works perfectly fine

 

[MK3Brent]

When you put the rings on, did you stagger the gaps?

 

[woodlandsrider]

When you put the rings on, did you stagger the gaps?

I did

 

[MK3Brent]

You need to do a leak down.

Create a fitting you can attach an air compressor to, then with the cylinder you choose, make sure the valves are closed and then pressurize the cylinder.

You will know once and for all if you have a piston ring seal.

Do not exceed the rated cylinder compression.

 

[Travis]

Zoom in and it is easier to read.