Re: 1979 CB750K with prolems

Posted by SoonerRon on
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/1979-CB750K-with-problems-tp3691671p3700201.html

I performed the leak down test last night on my old bike. I used a wrench to turn the crank to the 1-4 TDC mark and then the 2-3 TDC mark. I also used a screwdriver to probe through the sparkplug hole to verify each piston was at the top of its stroke before testing. #1 and #2 held good pressure with only minimal pressure loss past the rings. I could faintly hear the air escaping from the dipstick opening. Nothing from the exhaust or air breather that I could detect. #3 and #4, especially #3, both experienced rapid depressurization through both the intake and exhaust valves. I could feel the air escaping from the exhaust pipe and could hear air coming out of the air box. Couldn't really learn anything about the rings in those two cylinders, though, due to the condition of the valves. I would still like to get a compression reading on each cylinder. I hope to remove the engine from the bike in the next week or so and pull the head to get a look.

Thanks to everyone for the all the advice!