compression test

DevonCbx · Post by **DevonCbx** » Thu Nov 26, 2009 3:30 am

When checking the compression, do I need to make sure the valves are adjusted? Or can I get a proper compression reading before I take the valve cover off. All I want to do at this point is get a compression reading.

Thanks

alimey4u2 · Post by **alimey4u2** » Thu Nov 26, 2009 6:53 am

Sorry Duane, best make sure valve clearances are spot on PRIOR to compression test. You may be tilting at windmills if not...

daves79x · Post by **daves79x** » Thu Nov 26, 2009 7:30 am

The valves should at least be checked for close-to-proper specs. You certainly don't want one held open. But to get a proper compression reading, the engine should be warmed up. It is almost never possible to see compression readings to Honda's spec. They will usually be lower - sometimes a lot. If they are pretty even - that's what you want to see.

Dave

bobber · Post by **bobber** » Thu Nov 26, 2009 7:53 am

I'd check the compression first, using the readings as a baseline/comparison for the next 'must-do' step... checking valve adjustment... then re-check compression to see if the adjustment changed readings.
If there is a variance between final readings at least you'll have an idea as to whether a 'wet test' or compressed air(your choice) is needed to verify if the low reading caused by a burnt valve or worn rings.
When checking the compression throttle should be wide open for maximum air intake.
I've tried for years to hit Honda's compression spec's on my CBX's... never coming close getting best of 140.. now settled at 125-130. As long as the spec's are within 10% of one another and above 125 should be good. Only Honda unit I've been within compression spec was a Honda 50cc bike I re-ringed for my son years ago... that puppy almost hit 200lbs!!!! Guage stood straight up.