Kawasaki KZ650 cafe-racer. Valves leak test.

It may sound strange, but having the new OEM cylinder head and valves I decided to perform valves leak test. Therefore I installed all valves (without valve seals).

Then I performed a classic leak test using gasoline.

Intake valves seem to be tight, but couple of exhaust valves after some time shown signs of not complete tightness:

Then I performed the test in which combustion chambers are to be filled with liquid and compressed air are to be blown into intake and exhaust ports. I didn’t like the idea to use water on brand new valves so I filled the chambers with kerosene.

This test takes more activity from the tester, but it also shows results much quicker than classic test. It confirmed the result of the classic test. It’s likely that valves became tight during the work of the engine, but I didn’t wish   to take risks. I decided that even fine lapping compounds I have at hand will be coarse for the job, so I made my own compound from the mix of “coarse” polishing compound and oil. This soft “lapping” left no scratches but only shimmering traces on the valves and it did the trick, so all valves became tight.

Here is short video in before/after style. In second part I used improvised restrictor to create a pressure in ports.

Since I “lapped” every valve to a specific seat, now every set has it’s numbered compartment in the box I use for storing  cylinder head components. This box has seen quite a lot of valves, a very useful thing as it’s compartments could be easily  readjusted for 8 or 16 valves. Here it is with a set of parts ready for final assembling:

And to finish this part of the story here is a little illustration where curiosity could lead the man. So far I have three KZ750 cylinder head and one KZ650 cylinder head. Three of them have complete set of valve shims and one had only 7 shims. And when it came to making inventory of valve shims I became curious about shim sickness distribution. So I measured all shims, printed the table to fit shims and here we are:

Kawasaki KZ650-750 (including ZR750 Zephyr and ZR7) valve shims range from 2.00 to  3.20 so we could say that distribution of shims is slightly shifted from the centre to thinner ones.



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