Valve Lapping test

Hello kz heads
I opened a very low miles 1015 engine, it sat since 1978 in a basement and when I opened the engine the valves had issues due to humidity, the guy that I got it form spinn the engine and exhaust valve 2&3 where bended,I guess the shaft where rusted and the valve did not close completely and the piston hit it,
So I replaced the valves and did some lapping. How do know if the I did lap enough.How can I test if is ok before I assemble the engine that would be a mess,time and gaskets lost.
I remember a friend of mine use to put the head backward and put gasoline in them and if it was not going down he said was ok.
but I don remember if he did it straight away or overnight,and how acurate this test is.
any suggestions, I have assembled the head already but can surely rework on it.

Take a look at the Kawasaki Service Manual. It describes how to check the valves. If you do not own a manual click on the link below and go to Page 146. Read the section titled "Valve Seat Repair." Ed

www.kzrider.com/modules/ServiceManuals/K...Service%20Manual.pdf

Your friend's leak down test is a good idea, but if you're using petrol then it will evaporate off and will appear to go down.

You want to use a thin liquid - last time I did it I used engine degreaser. Lay the head on its back, fill up the chambers in the head, and go and have a coffee. Come back in 20 or 30 minutes, the level should not have gone down, provided it's not a liquid that evaporates quickly.

Best way is to prop the head up and pour petrol down the inlet and exhaust ports .
Obviously you can't do both IN and EX at the same time but you will know straight away if the valves are not seating.
No need to leave overnight.

A quick check is to stick a small flash light in the ports and look for light getting past the valves in a dark room

Using gasoline is how I was shown a long time ago, as a quick test of valve lapping. Gasoline is actually pretty hard to contain, and if you can pour gas in the port with the head sitting on the bench with the ports facing up with no leaking out immediately, you have a pretty good seal going on. Even a valve / seat that seeps a little gas will still run like a banshee, although no seepage is preferred.