its a 2004 400ex, i started the bike put it in the truck and brought it to my mechanic to lighten the flywheel and change the clutch and gasket. Now he calls me when hes finished and he says that the lights come on and when he presses the start button the lights turn off and a click is herd. Is that the mechanics prob or mine?

 

Weak voltage, loose connection(s), or corroded connection(s).
Only your mechanics problem if he had been working with which ever is found to be the culprit.

None of what he was working on required any mods to the ignition or charging system other than removing the negative battery cable before work was done,...which could be your answer right there. The problem doesnt sound bad to me.

 

Sounds to me like it is his problem. If you started it, put it in the truck and then he didn't start it until after performing the work then it may be yours. If they followed a manual, they always say to disconnect the battery before doing work. So, if they unhooked the battery and didnt get them tight when reconnecting it may just be a loose/dirty connection. But, wouldn't they have checked that? Good luck on this one!