Re: Loss of power 1979 CB750 - full throttle

Posted by robs750 on Jun 11, 2012; 6:24pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Loss-of-power-1979-CB750-full-throttle-tp4022506p4022771.html

A leakdown test is placing air into a cylinder to test the sealing of the valves,rings and headgasket.There are special gauges/regulator you could buy that show the percentage but are pricey.There is a flexible adaptor that screws into the spark plug thread.
With the piston at TDC and valves closed,you apply air pressure to the cylinder.If the valves are leaking, you will be able to hear air come out of the intake or exhaust or both.If the rings are bad,the air will escape into the crankcase.A bad head gasket will also show a air leak.
You can also do the test with an air compresser with a regulator to get a ball park check.