Should I check it with engine cold or hot?

 

slightly warm. Let it idle for like two minutes TOPS, then check. Squirt a couple drops of oil in the plug holes and spin it. Check it again.

If it is a newer bike, you must pull the fuse or disconnect the wiring for the ACRs. If it is a BAGGER, you must also hold the throttle plate open with your finger or a wooden dowel. Compression needs to be checked with WOT. DBW bikes will NOT open the throttle plate when checking compression.

 

Dont try to remove the spark plugs while the engine is hot!!!!

 

Thanks!

 

Or you can do it cold. I don't squirt oil in it. Definately have to open throttle plate.

 

The manual says to do it at operating temperature, but like soft02 says, removing the plugs from a hot aluminum head can cause problems. Personally, I would just do it at room temperature. If you're doing the compression check to troubleshoot some problem, chances are nearly 100% you'll find the problem hot or cold.

If you really want to do it hot, I'd remove the plugs first while it's cold, put some anti-seize on the plugs, reinstall and run up to temp. That would minimize any chances of damaging the threads in the head.