from zxforums;
"As many are aware there is an issue common to many 14's with the valve cover leaking. I recently had my valve adjustment done and during the procedure, with the help of Mike at Vista Kawasaki here in Dayton Ohio, I had the chance I needed to figure out what the real problem is. It is one of 2 things or a combo of both 1) the outer gasket is only about half the thickness of the gap it is supposed to seal, 2) the spark plug pass thru openings are cast unevenly and or, to long causing the valve cover to sit on the center gaskets way before the outer edge of the valve cover makes contact with the outer gasket.
I remedied the problem using the following fix if any one is interested in how to fix it correctly (so far ).
I had the gasket replaced a year ago under warranty but it still leaked so while the bike was apart I took the Gasket out and replaced the valve cover to find the gap to be almost 3mm and the gasket to be closer to 1 maybe 1.5mm. The cover is fairly flexible but would have to be deformed to be bent enough to put any real pressure on the gasket to seal it properly hence the leak.
The bolts used to hold down the cover have a shoulder on them that bottoms out on the block to prevent the cover from being overtightened and the gasket crushed (which isn't really a problem considering the gap they left) the gasket could have been thicker this would have solved the whole issue but as we all know getting Kawi to admit and rectify is another story all together.
Anyway many people will suggest adding washers to the bolts to raise the shoulder and allow the bolt to push the cover down further to seal against the gasket. There are a few problems with this suggestion 1) the cover is held up not only around the outside edge but also under each of the four spark plug pass thru locations which have individual gaskets under them which will be crushed or damaged with the extra pressure, 2) the cover will be deformed by pushing it down further than it was designed to and will flex at the center around the spark plug pass thru's instead of going down as a whole unit evenly causing uneven pressure around the edge on the gasket. 3) the cover will no longer be parallel to the block at the gasket due to the flexing and could result in the edge of the valve cover cutting the gasket if to much torque is applied, you even run the risk of cracking the cover as it is a cast part and will not bend much without cracking.
I put the valve cover on a CNC mill and faced off 30 thousandths of an inch (just under 1mm) also removed the same amount of material off the shoulders of the 6 bolts and the small tubular spacers that run next to the spark plug pass thru's for the smog valves. This allows the cover to sit down further and be tightened to where the bolt shoulders bottom out at the same time the outer gasket is compressed and the 4 spark plug pass thru gaskets are compressed also at the same time.
When I we took measurement across the 4 spark plug pass thru gasket surfaces they were off from one end to the other by almost .020" the result of a poor casting I'm sure. you can see in the photo where we milled off the material to let the cover sit down where it needs to be for the gasket they supply. A complex fix for a simple thicker gasket problem but since they don't have one this is the only real way to fix it."
So now the question is, if you replace the gasket with a thicker one, will it now leak at the spark plug gaskets?
Before your criticize someone, walk a mile in their shoes. That way, when you do criticize them, you're a mile away and have their shoes.