Do an old fashioned compression test. Remove all the plugs and conduct the test dry. Typical compression runs 110-150. What you want to see is the low reading being within 10 percent of the high reading. So if 150 is your high, you ideally want the lowest cylinder to be no lower then 135.
Once you do the test dry, do it over again but this time squirt a couple of good squirts of engine oil in just before you re run the test. The oil will form a temporary seal around the rings. If the compression raises noticeably, likely you have a ring problem. If it stays pretty close to the dry test, likely your blue smoke is the valve guides and missing crappy o ring valve seals. Pull the head and give it a good valve job and use so better valve seals.
