compression issues

Hello, I have a tapping sounds like a valve noise on my 1982kz1000j. I did a compression check a few days ago and not good. (cylinder 1) 75lbs, (cylinder 2) 45lbs, (3) 68LBS. and 110lbs in the 4th cylinder. The bike starts right up gives a small puff of smoke at the start but does not smoke afterwards. I know when valve seals leak on an old car it will give a puff of smoke to start with then subside. I guess i am wanting an opinion is this just a valve adjustment issue giving the terrible compression or is it something i have to go full out on. :full rebuild.Bore the cylinders out, oversized pistons, valve job etc. Any educated opinions?

A leak down test would be an excellent diagnostic method to determine general overall condition of the engine.

A leak down test injects air pressure through the spark plug hole to pressurize the combustion chamber.

Can perform a poor man's leak down test by introducing compressed air into a spark plug hole and listening to where it escapes from the combustion clamber. This may be done at TDC or any other cam positions where both valves are fully closed. Top dead center (TDC) is when the piston is at its highest position. An easy way to tell TDC is by alignment of the T mark with the case mark when viewed through the timing window.

May introduce a spurt of compressed air by using a rubber cone-tip blow gun (rubber air nozzle) held into the spark plug hole. And of course keep holding it in position to keep air from coming back out the spark plug hole while listening for escaping air at other places. The air compressor should not be running while listening because the noise will likely drown out any sound of escaping air. Or just use a portable compressed air tank.

Air heard escaping from exhaust port indicates exhaust valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from carb intake indicates intake valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from crankcase breather indicates loss of compression past rings into crankcase (perhaps worn piston rings or cylinders).

Air heard escaping from head gasket area indicates indicates loss of compression past head gasket (perhaps due to a blown head gasket).

A leaking valve may sometimes be resolved by adjusting the clearance to within specs.

A leaking head gasket may sometimes be resolved by torquing the head fasteners when the engine is stone cold (such as after sitting overnight).

Good Fortune!

I'll try tonight or tomorrow night. great info. thanks.
i will keep you informed.

Another interesting test is compression figures after inserting a teaspoon of motor oil into the combustion chamber through the spark plug hole, for the purpose of comparing with the "dry" compression test figures already determined.

If the added oil significantly increases compression, the otherwise too low compression probably results from something other than a leaking valve. Because compression would not build up and would instead leak out through the valve.

If the added oil fails to significantly increase compression, the low compression may result from a leaking valve. Because compression can't build up due to leaking out through the valve.

And important to remember that the compression test, dry or wet, does NOT guarantee that valve clearances are within specs. Because a valve with barely minimal clearance when cold, may completely seal, and then leak when the engine reaches normal operating temperature.

Should check the valve clearances (when engine is overnight stone cold), and adjust as may be found necessary to achieve factory spec.

Good Fortune!