I have no ignition spark,can any body point me in the direction to start looking for the cause?

 

Do you have a service manual for the quad? It is a very useful tool, especially in this circumstance.

The no spark instance is a very complicated means of testing - check the simple stuff first - - are you checking for spark with a new plug? Are there any obvious broken/torn wires? Have you shorted anything out?

Then you can get into component testing -
does the coil ohm out within specs? (primary - terminal on coil where blue/white wire connects to coil ground = 0.3 ohms) (secondary - spark plug cap removed - resistance from end of wire to coil ground = 6.3K ohms)
Then exciter and trigger coils - wires coming out of engine unplugged and measure resistance (on engine side connector) across:
red to green = 3.2 ohms (98 model)
black/red to green = 446 ohms

If these components are OK, then you most likely have a defective CDI module.

Hope this helps.