Compression Check Advice Needed

[jerry chabino]

Hi Guys,

I am restoring a 1977 KZ900. I have taken the old exhaust off and want to do a compression check. Question is can I do the compression check with the exhaust off or will it hose something up if I do ? Secondly, Do I have the throttle wide open when doing the compression check ?

Thanks,

Jerry

[cudaosix]

Plugs out, full throttle. If your going to ground your plugs by resting the plugs still attached to their leads on the cylinder head, tank off. Be ready for a small fire if you happend to spill any gas on the head. Safer way I think would be to unplug the hot wires from the coils (edit: just realized that unless you have aftermarket coils like dynas, you cant unplug anything, stock coils have the primary attached permantly to the coils). Some say it isnt necessary to ground at all. Your call. Not sure about the exhaust question, sorry.

[tnhunter]

The exhaust provides some back pressure to the cyclinder but only on the exhaust stroke. You want to measure the compression stroke, so it should not make any difference.

[zedx11]

I would leave the exhaust on. that is the way it runs and the way it should be tested.

[elr658]

The spark plug wires are called the SECONDARY. All plugs out.
Carbs off or throttle wide open. Primary side of coils disconnected. (As a Kawasaki will not let the motor turn over with kill switch off) Exhaust does not matter. Fully charged battery. Same number of rotations.