Re: 1979 CB750K with problems

Posted by shinyribs on
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/1979-CB750K-with-problems-tp3691671p3709057.html

If cylinder 3 is at zero pressure that suggest a valve leaking.If it had any rings at all you would get some sort of pressure.So you may just have a valve related issue rather than need to go into a huge rebuild.But you probably already knew that. I was told that 120 psi was the lowest acceptable pressure to run with but dont know that to be a fact.How many miles is on the bike?Also,if you do a compression check and do not open the throttle all the way the motor cannot ingest air effectively which will result in low readings.If you didnt test with the carbs in WOT position you may want to retry the test and see if the pressures come up.Also,i noticed that the pressure from 1-4 went higher and higher.If you tested them in that same order than the friction of turning the motor more and more as you went from cylinder to cylinder would explain the rising pressure as you went along.Just a thought.Best of luck to you.

Note:ingesting large doses of worm water while reading a compression gauge has been known to result in inaccurate "readings"