low compression

[CC260]

Going over the valk in preperation for a road trip and upon running a compression check all holes are showing only 90 PSI and the Honda manual calls for 171 PSI. This is with the engine at room temp and cranking with the starter. Battery is up fully charged. The engine runs well and gets around 33 MPG. I had to use threaded adaptors in the sparkplug holes to in order to use the comprssion gauge. The reason I checked it with the engine cold is that I have heard that you should not remove sparkplugs from an aluminum head when the engine is at operating temps. Is this true? Would the compressionbe higher with the engine warmed up? Looking for ideas about what I should do about the compression readings (If anything). Thanks for any and all ideas.   

[Chrisj CMA]

As far as I know diagnostic compression tests are only accurate at operating temp.  However you have some valuable diagnostic information...they were all showing 90 (the same) so whatever is the cause.....ill reading guage, cold motor, whatever, chances are you arent going to have a problem that gives a consistant reading like that.......so, since they were all the same, and it runs good, I say put the sparklers back in chalk it up to a cold motor and dont worry about it

PS....you are right about removing spark plugs on a hot motor (some) but I think the valk is not one that it matters.........I think you can remove a plug at operating temp no worries

[Patrick]

Not all compression gauges are created equal,,  there will be a difference between them.. The main concern is that all cylinders are about the same.. Now, concerning whether to perform the test hot or cold,, it should be performed 'warm' and technically the throttle should be open.. Maybe I've been doing this type of work for too long and I'm too old fashioned,, but,, sparklers should not be removed from a hot engine.. I've had to heli-coil too many holes from fellas doing just that.. So, my opinion, warm the engine, it doesn't take long, get the juices flowing, then re-do the test and see what happens.. I  have a funny feeling that you'll see a big difference.. These engines really don't have problems, they are pretty bulletproof..Oh, I'm also a big fan of never-seize in these circumstances..

[CC260]

Thanks for your replies. I do use anti seize and the plugs are easy to get out. Glad I didn't take them out with a hot engine. Think I will just ride and not worry over the compression. 

[Mr.BubblesVRCCDS0008]

Did you hold the throttle wide open while doing this test? You got to get air in there to compress. Just a thought.

[Pete]

90 is about right for a cold engine with the throttle closed, higher with the throttle open.

You are OK