Checking the clutch safety switch
For more information on the safety switches on the EX250, click here.
The purpose of the clutch safety switch is to make it so you can't start the engine in gear unless the clutch is pulled in. This keeps the bike from getting away from you when you try to start it. It also, in tandem with the sidestand switch, prevents riding away with the sidestand down.
When working properly, if your sidestand is down, bike is in gear, and clutch lever is squeezed, the bike will die as soon as you release the clutch lever. If you break off the plunger from the clutch switch, you can take off with the sidestand down, which is of course very dangerous. Don't ride with a broken clutch safety switch.
Your clutch switch is under the clutch lever. In this picture it's the rectangular piece right under the word 'lock'. You can see the plunger, which acts as an on/off switch, on the right of the switch (left side of the bike).
The first thing to check is the sound. When the clutch (or brake) lever is squeezed, the switch moves. The Kawasaki switches have a 'click' at the transition between off and on. Squeeze the brake a couple of times to listen for the 'click', then go to the clutch side and listen for the same noise.
If this checks out, do the following:
If the clutch switch is good, the engine will not crank over.
If you are able to hold the clutch lever in while the engine is running but, as soon as you start to release the lever, the engine turns off, that means it's the sidestand switch and not the clutch lever switch.
If it won't go into first with the sidestand down, regardless of the position of the clutch, chances are pretty good that the clutch safety switch is not working properly. If you have ever taken the lever off, chances are you broke the plastic plunger (see below).
If not, the switch is most likely bad. The bike won't start at all if the wiring harness is completely disconnected from the lever.
Testing the switch should take all of ten minutes with an ohmmeter. Here's how to go about that:
Physical: locate the switch. It's under the clutch lever. Examine it. If it has a black plunger sticking out of it which touches the hangy part of the lever (most visible when the lever is not pulled), the plunger is not broken.
Testing for switch function: follow the wires out of the switch to where they meet the wiring harness. Unplug the wiring harness. Take an ohmmeter (i.e... a multimeter set to "ohms", lowest range available if it is not auto-ranging) and stick the meter's probes into the middle and the left holes in the switch's plug. Pull and release the lever. The readout on the meter should change; in one position, it should be close to 0 ohms, in another position, it will be infinite. On an analog meter, 0 ohms is usually all the way to the right and infinite all the way to the left. On a digital meter, 0 is pretty obvious, infinite is usually something cryptic like "-0L" (consult meter manual for specifics). Now, test the middle and the right contacts. The behaviour should be the exact opposite.
If you don't get these readings, you may need to either clean or replace your clutch switch.