81 CB 750k dohc no compression.


New Member
Picked up a 81 750k engine looked great better than my 79.I got it home started to do some tests on it and it came up horrible on compression it had no compression on 1,2 60psi,3 90psi,4 90psi.I did notice with turning it over that the cam-to-cam chain was jumping all over.Started to pull it apart since it was a spare.Head was like brand new valves were great,Cams looked like brand new mild wear.Got down to the jugs all were less than than the wear limit like jugs had little to no wear on them Mic'd them by the way.Anyways i noticed large amounts of permatex between the mid section case grey on the outside and brown towards the inside.I pulled the Charging rotor and the end of the taper crank looked new no wear from rotor giving me the impression that it had never been changed.But the permatex is bothering me the factory would put a gasket there not form a gasket would they not?Odometer on bike it was pulled out of, said 25,000 but upper half of motor had all stock gaskets and had looked like it never been pulled apart.I'm thinking possible gear issues or primary replacement not sure.Any ideas on the form a gasket material?


Over 10,000 Posts
Factory used 3 bond applied thinly.

As Joe mentioned, if cam timing is off it may not have much compression. With the head assembled and no cams, pour gas into each combustion chamber and see if it leaks past the valves. Or rig up a vacuum gauge (mityvac is fine) and plugs and see if each port will hold a vacuum.

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